/'BERKELEY* LIBRARY
I UNIVERSITY OF \CAUFORNIA
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EARTH
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Olarnegte Utbrarg
WITHDRAWN WILLS COLLEGE LIBRAS/
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MARYLAND GEOLOGICAL SURVEY
UPPER CRETACEOUS
TEXT AND PLATES
MARYLAND
GEOLOGICAL SURVEY
UPPER CRETACEOUS
TEXT AND PLATES
EARTH
SCIENCE?
LIBRARY
rs
EARTH CLASS PELECYPODA (CONT.NUBD) S5!?1
Subgenus GRYPH/EOSTREA Conrad [Am. Jour. Conch., vol. i, 1865, p. 15. Name only]
Type. — Ostrea subeversa Conrad = Gryphcea vomer Morton.
" Shell thin, elongate, straight, narrow ; lower valve rather deep and smooth; upper valve flat or slightly concave, and ornamented with distant, ' regular, thin, concentric laminae; beak of lower valve contorted, or turned to one side ; cartilage-pit narrow, oblique. — Gryphcea vomer Morton (sp.). Mr. Conrad did not publish a diagnosis of this type, but merely gave the name in a list of fossils. At my request, however, he gave me in manuscript the above diagnosis, and mentioned the above type. I would add that, in perfectly preserved specimens, the typical species presents the singular peculiarity of throwing out long, slender, auricular appen- dages (one on each side) from the lower valve near the beak. These being very fragile, are nearly always broken away, as the specimens are found; but I observed several, with more or less of them preserved, in the New Jersey beds ; and one I found growing in the inside of a Gryphcea vesicu- laris with them perfectly preserved and apparently attached to the Gryphcea by their extremities." — Meek, 1876.
Gryphceostrea suggests Exogyra in the gyrate umbones of the left valve, The beak of the right valve of the former, however, is orthogyrate or at the most slightly inclined, and this, together with the inflation of the beak of the left valve, allies it more closely with Gryphcea than with Exogyra.
(GRYPH^OSTREA) VOMER Morton Plate XXV, -Figs. 1-4
Gryphcea vomer Morton, 1828, Jour. Acad. Nat. Sci., Phila., vol. vi, p. 83. Gryphcea vomer Morton, 1834, Syn. Org. Rem. Cret., p. 54, pi. ix, fig. 5. Gryphcea vomer Conrad, 1835, Trans. Geol. Soc., Pennsylvania, vol. i, p. 336. Gryphcea vomer Conrad, 1842, Proc. Nat. Inst., Bull, ii, p. 172. Exogyra lateralis Meek, 1864, Check List Inv. Fossils N. A., Cret. and Jur.,
p. 6. Ostrea (Gryphceostrea) subeversa Conrad, 1865, Am. Jour. Conch., vol. i,
p. 15 (name only).
Etymology: 7pii7r6y, hook-nosed; ostrea, oyster.
580 SYSTEMATIC PALEONTOLOGY
Gryphceostrea lateralis Conrad, 1868, Cook's Geol. of New Jersey, p. 724. " Ostrea lateralis Nilsson " Coquand, 1869, Mon. Genre Ostrea, p. 96, pi. xxx,
fig. 10. (Not Ostrea vomer d'Orbigny, 1850, Coquand, Mon. Genre
Ostrea, p. 39, pi. xvi, figs. 13-15. = 0. 'convexa Say.)
Gryphceostrea vomer Meek, 1876, Kept. U. S. Geol. Survey, Terr., vol. ix, p. 11. Ostrea vomer White, 1884, 4th Ann. Kept. U. S. Geol. Survey, p. 302, pi. xlviii,
figs. 8-10. Gryphceostrea vomer Whitfield, 1885, Mon. U. S. Geol. Survey, vol. ix, p.
195, pi. xxvi, figs. 11, 12.
Ostrea sp. Clark, 1895, Johns Hopkins Univ. Circ., vol. xv, p. 6. Ostrea sp. Clark, 1896, Bull. 141, U. S. Geol. Survey, p. 88, pi. xxxix, figs.
3a-3c.
Ostrea subeversa Clark, 1896, Bull. 141, U. S. Geol. Survey, p. 93. Ostrea (Gryphceostrea) subeversa Ball, 1898, Trans. Wagner Free Inst. Sci.,
vol. iii, pt. iv, p. 681. Ostrea (Gryphceostrea) vomer Clark, 1901, Md. Geol. Survey, Eocene, p. 193,
pi. 1, figs. 1-5. Ostrea (Gryphceostrea) vomer Johnson, 1905, Proc. Acad. Nat. Sci., Phila.,
p. 11. Gryphceostrea vomer, Weller, 1907, Geol. Survey of New Jersey, Pal., vol.
iv, p. 455, pi. xliv, figs. 7-11. (Exclude fig. 6, broken valve of Gryphcea
vesicularis) .
Description. — " Shell subrhomboidal ; upper valve small, thin, slightly concave ; lower valve convex, obscurely lobed, the lobed margin obliquely produced from the hinge ; a wrinkled groove each side of the latter ; beak pointed, curved obliquely inwards ; umbo prominent." — Morton, 1828.
Type Locality. — New Egypt, New Jersey.
Shell of moderate size, elongate, rudely ovate or elliptical, strongly inequivalve ; attached left valve strongly convex, often irregular in outline over the area of attachment in the umbonal region ; umbones inflated, tips prosogyrate and acutely pointed, when not flattened against the sup- porting surface; anterior and posterior dorsal margins of perfect and typically developed individuals produced into long, slender, auricular extensions somewhat similar to those of Gryphcea convexa Say. External surface of left valve smooth excepting for growth striations, right cover- valve regularly subovate, flattened, often a little sinuous and with a slight forward twist in the flattened umbonal region; external surface sculptured with conspicuous, fine-edged concentric laminas, five to eleven in number, regularly spaced, parallel to the outer margin and delimiting the outline of the shell during former stages of growth ; hinge area small,
MARYLAND GEOLOGICAL SURVEY 581
low, flattened as a rule, irregular in outline, submargins auriculately produced in the left valve, somewhat thickened but not produced in the right valve ; not sculptured ; muscle impressions elongated, rudely semi- elliptical, concentrically striated.
The characters of the attached valve of G. vomer are variable, the inflated umbones and smooth external surface constituting perhaps the best diagnostic of indifferently preserved individuals. The ovate outline and the elevated concentric lamina are sufficient to determine even a fragment of the right valve.
Occurrence. — M ATA WAN FORMATION. ? Gibson's Island, ? head of Magothy River, ? Ulmstead Point, Anne Arundel County, Maryland. MONMOUTH FORMATION. Two miles west of Delaware -City on John Hig- gins farm, Briar Point, Post 156, Chesapeake and Delaware Canal, Dela- ware; Bohemia Mills, Cecil County; mouth of Turner's Creek, Kent County; Brightseat, railroad cut west of Seat Pleasant, Brooks estate near Seat Pleasant, Friendly, and McNeys Corners, Prince George's County, Maryland. EANCOCAS FORMATION. Noxontown Pond, Delaware.
Collections. — Maryland Geological Survey, Philadelphia Academy of Natural Sciences, New Jersey Geological Survey, U. S. National Museum.
Outside Distribution. — Matawan Formation. Marshalltown clay marl, New Jersey. Monmouth Formation. Navesink marl and Red Bank sand, New Jersey. Rancocas Formation. Vincentown limesand and Horners- town marl, New Jersey. Eutaw Formation (Tombigbee sand member). Exogyra ponderosa zone, Lee and Alcorn counties, Mississippi. Eipley Formation. Exogyra costata zone, east-central and northern Mississippi. Extreme top of zone, Union County, Mississippi. Selma Chalk. Exogyra ponderosa zone, Warrior and Tombigbee rivers and Pickens County, Ala- bama; east-central and northern Mississippi and Tennessee. Exogyra costata zone, Sumter and Wilcox counties, Alabama; east-central and northern Mississippi. Nanjemoy Formation. Maryland. Aquia Forma- tion. Maryland. Jackson Formation. Alabama.
582 SYSTEMATIC PALEONTOLOGY
Superfamily TRIGONIACEA
Family TRIGONIIDAE
Genus TRIGONIA Bruguiere [Ency. M6th. Vers., vol. I, 1789, p. xiv]
Type. — Trigonia margaritacea Lam.
Shell heavy, nacreous within, equivalve, inequilateral, subtrigonal or trapezoidal in outline. Umbones anterior, opisthogyrate, moderately inflated, lunule absent, escutcheon strongly defined; posterior area sharply differentiated by a carina extending from the umbones to the posterior ventral margin ; sculpture upon medial and anterior portions of the disk usually developed and often more or less nodose ; sculpture upon the pos- terior area concentric, radial, divaricate, or absent. Hinge dentition vigorous, two divergent transversely striated cardinal teeth in the right valve, three cardinals in the left, the middle tooth stout, trigonal, medially sulcate, transversely striated, the two outer cardinals compound and rela- tively small, transversely striated within. Ligament groove marginal, opisthodetic, muscle impressions two in number, the posterior the larger, pallial line indistinct, entire.
Trigonia was one of the major elements during the Mesozoic, the epoch which marks its origin and culmination. Five species still persist in the Australian region, but they are rather distantly connected with the Meso- zoic forms.
A. Costals not exceeding 16 in number Trigonia eufalensis
B. Costals exceeding 16 in number.
1. Shell semi-elliptical in outline, not rostrate posteriorly, costals
coarser upon the medial portion of the shell than towards the extremities Trigonia cerulea
2. Shell trigonal in outline, rostrate posteriorly, costals conspicuously
coarser on the anterior third of the shell, becoming abruptly finer and more regular in arrangement medially.
Trigonia marionensis
TKIGONIA EUFALENSIS Gabb Plate XXXIV, Figs. 1, 2
Trigonia eufalensis Gabb, 1860, Jour. Acad. Nat. Sci., Phila., 2d ser., vol. iv,
p. 396, pi. Ixviii, fig. 32. Trigonia eufalensis Meek, 1864, Check List Inv. Fossils, N. A., Cret. and
Jur., p. 9.
Etymology: Tpi, three; ywvia, angles.
MARYLAND GEOLOGICAL SURVEY 583
Trigonia eufalcnsis Conrad, 1868, Cook's Geol. of New Jersey, p. 725. Trigonia eufalensis Whitfield, 1885, Mon. U. S. Geol. Survey, vol. ix, p. 113,
pi. xiv, figs. 1-4.
Trigonia eufalensis Johnson, 1905, Proc. Acad. Nat. Sci., Fhila., p. 11. Trigonia eufalensis Weller, 1907, Geol. Survey of New Jersey, Pal., vol. iv,
p. 462, pi. xlviii, figs. 5-10.
Description. — " Subtriangular, resembles T. alceformis Sow. in out- line, not quite so elongate anteriorly; beaks posterior; lunule distinct; surface marked by about fourteen ribs, the more anterior of which pro- ceed from the lunule anteriorly and then cross the shell at right angles with the lunule, exhibiting a tendency to being nodose, especially near the lunule; lunule marked by ten or twelve transverse ribs; cardinal margin somewhat incurved, anterior elongate and subbiangular, basal sinuous and deeply serrate, posterior regularly rounded ; internally, hinge teeth small, muscular impressions deep ; pallial line entire ; a small tooth- like ridge or process extends along the middle of the alation, as in T. alceformis." — Conrad, 1860.
Type Locality. — Eufaula, Alabama.
Shell thick, heavy, prismatic, rudely trigonal in outline, moderately convex ; umbones anterior, incurved, opisthodetic, flattened upon their summits but prominent by reason of their position at the apex of an angle of approximately 120° ; lunule not differentiated, escutcheon denned, not only by the sculpture but also by an abrupt change in the plane of the shell ; anterior portion of the shell sculptured by twelve to fifteen promi- nent concentric ridges, rather sharply rounded upon 'their summits, dor- sally inclined, especially in the umbonal region, more prominent, sym- metrical and feebly rugose ventrally, regularly arranged but much more closely spaced along the concave margin than the convex ; ligament mar- ginal— the groove in which it was lodged short linear and opisthodetic; cardinal teeth of left valve massive, trigonal, transversely striated, inner faces of hinge margins also striated in order to clasp the divergent teeth of the right valve ; muscle impressions deeply excavated, the anterior slightly more so than the posterior; pallial line simple — distant from the hinge margin.
584 SYSTEMATIC PALEONTOLOGY
This species is the smallest and most abundant member of this remark- able genus within the confines of Maryland. It is separated from T. cerulea Whitfield by the more prominent umbones, the more convex posterior dorsal, the more attenuated posterior extremity and the fewer rugose and relatively coarser external costae.
Occurrence. — MONMOUTH FOTIMATIOX. ? 2 miles west of Delaware City on John Higgins farm, Delaware ; ? Bohemia Mills, Cecil County ; mouth of Turner's Creek, Kent County; Brightseat, Brooks estate near Seat Pleasant, Friendly, 1 mile west of Friendly, McNeys Corners, Fort Washington, Prince George's County, Maryland.
Collections. — Maryland Geological Survey, Philadelphia Academy of Natural Sciences, New Jersey Geological Survey, U. S. National Museum.
Outside Distribution. — Matawan Formation. Merchantville clay marl, Woodbury clay and Wenonah sand, New Jersey. Black Creek Formation. North and South Carolina. Peedee Sand. North and South Carolina. Eutaw Formation (Tombigbee sand member). Exogyra ponderosa zone, Mortoniceras subzone, Georgia. Ripley Formation. Exogyra costata zone, Georgia ; Eufaula, Alabama. Extreme top of zone, Pataula Creek, Georgia.
TRIGONIA CERULEA Whitfield
Trigonia cerulea Whitfield, 1885, Mon. U. S. Geol. Survey, vol. ix, p. 114, pi.
xiv, fig. 7. Trigonia cerulea Weller, 1907, Geol. Survey of New Jersey, Pal., vol. iv, p.
464, pi. xlviii, fig. 13.
Description. — " Shell small or below a medium size, moderately convex on the valves and of a triangularly-ovate outline. Beak small, appressed, obtusely pointed and erect; posterior hinge-line long and slightly con- cave ; posterior end narrow and rounded ; anterior end broadly rounded ; basal line a litle gibbous in the middle, but otherwise forming a continuous line with the anterior and posterior margins. Surface of the shell cov- ered by coarse elevated ribs, which are flattened on their surfaces over a large part of the shell, but near the posterior cardinal margin are sharp and very slightly crenulated. The ribs are coarse and distant on the ante- rior and middle parts of the shell, but gradually become finer and more
MARYLAND GEOLOGICAL SURVEY 585
closely arranged toward the posterior part. Interspaces concave. No postero-cardinal area is visible on the specimen used, the ribs apparently passing, without interruption, across the entire disk of the shell and ter- minating on the cardinal margin. The ribs of the anterior end curve strongly forward in passing to the basal and anterior margins, while those of the hinder parts of the valves pass more directly across to the postero- basal margin. This species differs from any of the others described from these beds in its form, but more particularly in the style and number of the surface ribs. They are more numerous than on any of the other forms, there having been about twenty-three on the specimen figured, which is only one inch and an eighth in length. Their flattened surface and the gradual increase backward is also opposite from that which is seen to occur on those .... In coarse olive-green indurated marl at the deep cut on the Holmdel and Keyport Turnpike, Monmouth County, New Jersey, at the base of the Lower Marls. The substance of the shell is entirely changed to vivianite, which is soft and of a bright blue color, very easily destroyed by handling or rubbing." — Whitfield, 1885.
This species is represented in the collections of the Maryland Cretaceous by a single valve. The species is somewhat larger than the more common T. eufalensis Gabb, is less trigonal and more semi-elliptical in outline, not rostrate posteriorly and less coarsely and more uniformly sculptured.
Occurrence. — MONMOUTH FORMATION. Brooks estate near Seat Pleas- ant, Prince George's County.
Collections. — Maryland Geological Survey, Columbia University, New Jersey Geological Survey.
Outside Distribution. — Monmouth Formation. Tinton beds, New Jersey.
TRIGONIA MARIONENSIS Stephenson n. sp.
Description. — " Shell subtrigonal, equivalve, inequilateral, moderately ventricose anteriorly, becoming strongly compressed posteriorly; beak small, incurved, situated about one-quarter the length of the shell from the anterior extremity. Hinge and dorsal area too poorly preserved for description.
586 SYSTEMATIC PALEONTOLOGY
" Posterior adductor scar apparently small and situated near the dorsal margin, at about the mid-length of the shell; a sharp crested ridge or carina extends from a short distance behind this scar backward to about the middle of the posterior extremity. Dorsal margin broadly concave ; anterior margin broadly and regularly rounded; ventral margin regu- larly rounded anteriorly, notched, the notches corresponding to the interspaces between the ribs ; the broad curve carries the ventral margin upward toward the high narrow posterior portion of the shell, where the margin curves slightly downward becoming concave, and meeting the posterior margin in a subright angle : posterior margin short, squarely truncated, and situated above the mid-height of the shell.
" Surface of the adult marked by 20-22 prominent ribs which originate along the lower margin of the dorsal area and extend to the anterior and ventral margins; the ribs on the anterior portion of the shell trend first forward and downward, and then sweep in a gentle curve around to the anterior margin; from the front toward the rear the ribs become suc- cessively straighter, tending first downward, and, toward the posterior extremity, backward and downward ; the crests of the ribs are poorly pre- served but are apparently tuberculated.
"Dimensions.— Length 37 mm.; height 27 mm.; convexity 7 mm.
"' This species differs from Trigonia eufaulensis Gabb in the closer spacing and smaller degree of curvature of the ribs, and in the greater curvature of the ribs, and in the greater elongation of the posterior portion of the shell. The species is distinguished from the young of Trigonia bartrami by the relatively closer spacing of the ribs and the greater pos- terior elongation of the shell.
"Type.—U. S. National Museum, No. 31642.
" Occurrence in South Carolina. — Snow Hill member of Black Creek formation (upper part of Exogyra ponderosa zone). Hodge's old mill site, 3^ miles southeast of Mullins, Marion County.
"' Occurrence in Alabama. — Tombigbee sand member of Eutaw forma- tion (lower part of Exogyra ponderosa zone). Seaboard Air Line Kail- way at bridge over Hatchechubbee Creek, 2 miles west of Pittsview, Russell County." — Stephenson, MS.
MARYLAND GEOLOGICAL SURVEY 587
Occurrence. — MATAWAN FORMATION. North shore Round Bay, Severn River, Anne Arundel County. MOXMOUTH FORMATION. Millersville, Anne Arundel County.
Collections. — Maryland Geological Survey, U. S. National Museum.
C. Isodonta
Superfamily PECT1NACEA Family PECT1NIDAE
Genus PECTEN Miiller [Zool. Dan Prodr., 1766, p. 248]
Type. — Ostrea maxima Linne.
Shell approximately equilateral, inequivalve, usually suborbicular, auriculate; right valve, as a rule, the more convex, not adherent but attached by a byssus; hinge line straight; resilium central, internal, tri- angular ; interlocking grooves and ridges diverging from the apex of the resilial pit; pallia! line simple; monomyarian; adductor impression rounded, posterior.
The earliest Pecten known is from the Cretaceous. The recent species exceed two hundred in number and their distribution is world-wide.
A. Shell not conspicuously inequivalve.
1. External surface radially sculptured.
a. Radial sculpture of more or less arcuate linear lirse.
Pecten argillensis
b. Radial sculpture coarse to fine but not linear nor arcuate.
i. Adult shell exceeding 3 cm. in diameter; radials not sul- cate, more or less scabrous, 30 to 40 in number.
Pecten whitfieldi
ii. Adult shell not exceeding 3 cm. in diameter; radials medially sulcate, as a rule, but not scabrous, 12 to 18 in number Pecten venustus
2. External surface not radially sculptured.
a. External surface faintly sculptured concentrically.
i. Adult shell exceeding 2 cm. in diameter.
Pecten cliffwoodensis ii. Adult shell not exceeding 2 cm. in diameter. .Pecten conradi
b. External surface smooth, adult shell not exceeding 2 cm. in
diameter Pecten simplicius
B. Shell conspicuously inequivalve Pecten guinquecostatus
Etymology: Pecten, a comb. A reference to the series of small tooth-like spines placed on the margin of the shell at the byssal opening.
39
588 SYSTEMATIC PALEONTOLOGY
PECTEN AEGILLENSIS Conrad Plate XXXIV, Figs. 3-5
Pecten argillensis Conrad, 1860, Jour. Acad. Nat. Sci., Phila., 2 ser., vol.
iv, p. 283. Pecten argillensis Meek, 1864, Check List Inv. Fossils, N. A., Cret. and Jur.,
p. 7. Camptonectes bellisculptus Conrad, 1869, Am. Jour. Conch., vol. v, p. 99, pi.
ix, fig. 11. Camptonectes (Amusiumj burlingtonensis Whitfield, 1885, Mon. U. S. Geol.
Survey, vol. ix, p. 53, pi. viii, figs. 3-7, 9 (not fig. 8) (ex parte) ; not
Pecten burlingtonensis Gabb, 1860.
Pecten bellisculptus Johnson, 1905, Proc. Acad. Nat. Sci., Phila., p. 11. Pecten argillensis Weller, 1907, Geol. Survey of New Jersey, Pal., vol. iv,
p. 472, pi. xlix, figs. 1-4.
Description. — " Suborbicular, very thin, compressed ; radiated only on the upper part with minute lines ; disk covered with closely arranged, fine lamelliform striae, except on the umbo and adjacent parts where they are distant; posterior margin opposite the ear carinated. (Upper valve.)" — Conrad, 1860.
Type Locality. — Owl Creek, Tippah County, Mississippi.
Shell rather thin and fragile, compressed, subequivalve ; outline, exclu- sive of the auricles, a sector of approximately 90° ; hinge line straight, a little more than half as wide as the shell; auricles broad but rather low; surface ornamentation elaborate but not conspicuous, radial sculpture of finely incised lines, two to four to the millimeter, on the disks of the adults, straight in the medial portion but sweeping in gentle curves toward the lateral margins deeper and a little broader posteriorly than anteriorly; concentric lines thirty to forty in number, over-riding and intercepting the radials, finely and evenly crenulated and in the umbonal region of perfectly preserved adults, minutely moniliform; auricles very unequal, the anterior broader and relatively lower than the posterior; posterior auricle sculptured with approximately fifteen coarse lirations running oblique to the hinge margin, rendered minutely scabrous by the over-riding incrementals ; anterior auricle long and narrow, alate in outline, the striations radiating from the umbonal extremity, sweeping in rather abrupt curves to the dorsal margin; byssal sinus narrow and very
MARYLAND GEOLOGICAL SURVEY 589
deep ; the area between the auricle and the disk not sculptured ; characters of interior not known.
Pecten argillensis is identical with Pecten bellisculptus Conrad, which was doubtless described from a type on which the delicate beaded sculpture was better preserved than on the type of P. argillensis Conrad. The species is one of the most abundant representatives of its genus in Mary- land, but unfortunately it is so fragile that perfectly preserved individuals are obtainable only with the greatest difficulty.
Occurrence. — MONMOUTH FORMATION. Brightseat, Brooks estate near Seat Pleasant, 1 mile west of Friendly, Prince George's County.
Collections. — Maryland Geological Survey, Philadelphia Academy of Natural Sciences, New Jersey Geological Survey, U. S. National Museum.
Outside Distribution. — Matawan Formation. Merchantville clay marl, Woodbury clay, Marshalltown clay marl, and Wenonah sand, New Jersey. Monmouth Formation. Navesink marl, New Jersey. ? Black Creek Formation. North and South Carolina. Eutaw Formation (Tombigbee sand member). Exogyra ponderosa zone, Mortoniceras subzone, Lowndes County, and ? Prentiss County, Mississippi. Ripley Formation. Exo- gyra costata zone, Georgia; Eufaula, Alabama; Chickasaw, Union and Tippah counties, Mississippi. Extreme top of zone, Pataula Creek, Georgia; Chattahoochee River, Alabama; Lowndes and Union counties, Mississippi.
PECTEN WHITFIELDI Weller
Pecten tenuitestus Whitfield, 1885, Mon. U. S. Geol. Survey, vol. ix, p. 47, pi. vii, figs. 5, 6. (Not Pecten tenuitestus Gabb, 1862.)
Pecten wMtfieldi Weller, 1907, Geol. Survey of New Jersey, Pal., vol. iv. p. 468, pi. 1, fig. 14.
Description. — " Shell of small to medium size, broadly ovate exclusive of the auriculations, the breadth of the shell being to the height as six is to seven. Cardinal slopes straight, more than one-third the length of the shell, and the anterior longest. Left valve very depressed convex, most ventricose above the middle ; beak small and pointed. Auriculations large, the anterior double the size of the posterior, very slightly rounded on the
590 SYSTEMATIC PALEONTOLOGY
margin, and perceptibly narrowing below; posterior shorter on the car- dinal line than below; anterior side marked by seven sharply-elevated nodose rays, and the posterior by six, with one or two smaller ones between, near the body of the shell. Body of the shell marked by about thirty to thirty-five slender, rounded but unequal rays with much wider flattened interspaces, with an occasional incipient ray on the outer third of the shell. Ribs marked by distant, elevated or subspinose nodes, most closely arranged on the auriculations and obsolete above the middle of the body of the valve. Right valve with the ribs proportionally stronger in the specimens examined than on, the left valve and showing a stronger ten- dency to alteration of smaller and larger ones than on the opposite, while the imbrications of the ribs are not nearly so strong, not rising into spines, as on the left valve. Auriculations of the right valve scarcely perceptibly radiate, while the concentric markings of the valve are more subdued throughout.
" So far as I have discovered the species was never figured by its author, but its description is more full than usual, so I think the identification is less Mkely to be questionable than in some other instances. It would seem to be the type of Pecten islandicus, although the ribs are less closely arranged and the interspaces are flattened. Among the few specimens which I have examined I have seen no reason to suppose the valves were so strongly bent as to leave them ' about half an inch apart in the middle/ as the author states.
"Formation and Locality. — In the Lower Green marls at Holmdel, New Jersey, collected at G. C. Schanck's pits, near Marlborough, and pre- sented to the New Jersey collection by the Rev. Dr. Riley. It also occurs at Burlington, New Jersey." — Whitfield, 1885.
" Shell, exclusive of the auriculations, broadly ovate in outline, higher than wide, the dimensions of a left valve being: height 40 mm., width 35 mm., convexity 5 mm., length of hinge-line about 16 mm. Left valve depressed convex, deepest above the middle, the beak pointed, auriculations of moderate size, the anterior one larger than the posterior. Surface marked by low, rounded, nodose, more or less unequal, radiating ribs, which increase by intercalation, thirty or more are present upon the body
MARYLAND GEOLOGICAL SURVEY 591
of the shell where they are narrower than the interspaces, the ribs upon the auriculations are narrower, closer together, and more nodose than upon the body of the shell, though in some examples, especially the larger ones, they are inconspicuous. The surface is also marked by more or less irregular, concentric lines of growth.
"Remarks. — The shells which are made the types of this species were identified and illustrated by Whitfield as P. tenuitestus, but an exami- nation of Gabb's type of that species has shown that Whitfield's identifica- tion was incorrect, the true P. tenuitestus being the same as the specimens described as P. planicostatus by that author. This species differs from P. tenuitestus of the same fauna, in being proportionally higher, nar- rower, and more convex, with the radiating ribs nodose, and proportion- ally broader with narrower interspaces and with the concentric markings coarser and less regular." — Weller, 1907.
A fragment of a nmlticostate scabrous Pecten occurs at Brooks estate, Prince George's County, and may perhaps indicate the former presence of this species in Maryland. Fragments of another species, possibly closely allied with P. whitfieldi Weller, were collected in the Matawan at Camp Fox on the Chesapeake and Delaware Canal. The Matawan form has much more numerous costa3 which are rendered scabrous by the over- riding concentric sculpture.
Occurrence. — MOXMOUTH FORMATION. Brooks estate near Seat Pleas- ant, Prince George's County.
Collections. — Maryland Geological Survey, Columbia University, New Jersey Geological Survey.
Outside Distribution. — Monmouth Formation. Navesink marl, New Jersey.
PECTEX VEXUSTUS Morton Plate XXXIV, Figs. 6, 7
Pecten venustus Morton, 1833, Am. Jour. Sci., 1st ser., vol. xxiii, p. 293, pi.
v, fig. 7. Pecten venustus Morton, 1834, Syn. Org. Rem. Cret. Group, U. S., p. 58, pi.
v, fig. 7. Pecten venustus Meek, 1864, Check List Inv. Fossils, N. A., Cret. and Jur.,
p. 7.
592 SYSTEMATIC PALEONTOLOGY
Pecten venustus Conrad, 1868, Cook's Geol. of New Jersey, p. 725.
Pecten venustus Whitfield, 1885, Mon. U. S. Geol. Survey, vol. ix, p. 45, pi.
vii, figs. 1, 2.
Pecten venustus Johnson, 1905, Proc. Acad. Nat. Sci., Phila., p. 11. Pecten venustus Weller, 1907, Geol. Survey of New Jersey, Pal., vol. iv, p.
478, pi. li, figs. 1-5.
Description. — " Shell thin, depressed, about half an inch in diameter, with fifteen or twenty double costae; those on the lower valve delicately beaded. From New Jersey." — Morton, 1833.
Shell small, rarely more than a centimeter and a half in diameter, more than moderately inflated, subequilateral excepting for the auricles, a little higher than wide, dorsal margins converging at an angle of approxi- mately 90°, lateral ventral margins roughly subscribing the major portion of a circle; external surface sculptured with some fifteen radial costae broader toward the ventral margin and for the most part medially sulcate, interradials deeply channeled, usually narrower than radial s; auricles unequal, the posterior smooth and rudimentary, the anterior narrow, elon- gate, distally truncate, sculptured with four or five subequal lirae ; byssal notch rather shallow; interior plicated in harmony with the eternaxl sculpture.
Pecten venustus Conrad is the only one of the small Pectens that develops a vigorous radial sculpture.
Occurrence. — MATAWAN FORMATION. Post 236, Camp Fox, Post 218 and Post 192, Camp U & I, Chesapeake and Delaware Canal, Delaware.
Collections. — Maryland Geological Survey, Philadelphia Academy of Natural Sciences, U. S. National Museum.
Outside Distribution. — Matawan Formation. Marshalltown clay marl, New Jersey. Monmouth Formation. Navesink marl, Eed Bank sand and Tinton beds, New Jersey. Ripley Formation. Exogyra costata zone, Chickasaw and Union counties, Mississippi. Selma Chalk. Exogyra cos- tata zone, Sumter County, Alabama ; east-central Mississippi.
PECTEN CLIFFWOODENSIS Weller
Pecten cliffwoodensis Weller, 1907, Geol. Survey of New Jersey, Pal., vol. iv, p. 469, pi. 1, figs. 7, 8.
MARYLAND GEOLOGICAL SURVEY 593
Description. — " The dimensions of an average specimen, a left valve, are : Height 30 mm., width 27.5 mm., convexity 4 mm., length of hinge line 14 mm. The body of the shell broadly subovate in outline ; the beaks situated a little back of the middle of the hinge line, the auriculations mod- erately large and sharply differentiated, the anterior ones somewhat larger than the posterior, the cardinal slopes diverging from the beak at an angle of 90° or a little more, nearly straight or slightly concave, terminating at the sides of the shell above the middle of its height. The valves sub- equally depressed convex, the right valve if anything slightly flatter than the left, with a moderately deep byssal sinus. Surface of both valves nearly smooth, marked only by fine concentric lines of growth which continue across the auriculations, and on the anterior ear of the right valve become stronger than elsewhere on the shell. One imperfect specimen which seems to be a member of this species had a height, when complete, of about 50 mm., but the dimensions given above are those of a specimen of about average size. Some of the smaller individuals do not exceed 12 mm. in height. With the growth of the shell the proportionate width seems to increase. This species is unlike any of the other Pectens in these New Jersey faunas, but in general form and size the shells most closely resemble some individuals of Pecten bellisculptus Con. ; the two species can always be distinguished, however, by their surface markings." — Weller, 1907.
Type Locality. — Cliffwood Point, Middlesex County, New Jersey.
A cast of a single valve which presents no characters by which it can be separated from Pecten cliffwoodensis Weller was collected at Arnold Point, on the Severn River in Anne Arundel County.
Occurrence. — MATAWAN FORMATION. North shore Eound Bay, Severn Eiver, Anne Arundel County.
Outside Distribution. — Magothy Formation. Cliffwood clay of New Jersey.
PECTEN CONRADI (Whitfield) Johnson
Pecten simplicus Conrad, 1868, Cook's Geol. of New Jersey, p. 725.
(Not Pecten simplicius Conrad, 1860, Jour. Acad. Nat. Sci., Phila., 2d
ser., vol. iv, p. 283, pi. xlvi, fig. 44.) Sinsyclonema f simplicia Conrad, 1869, Am. Jour. Conch., vol. v, p. 99, pi. ix,
fig. 20.
594 • SYSTEMATIC PALEONTOLOGY
Amusium conradi Whitfield, 1885, Mon. U. S. Geol. Survey, vol. ix, p. 52,
pi. vii, figs. 8-10.
Pecten conradi Johnson, 1905, Proc. Acad. Nat. Sci., Phila., p. 12. Pecten conradi Weller, 1907, Geol. Survey of New Jersey, Pal., vol. iv, p.
474, pi. 1, figs. 1-4.
Description. — " Shell small, seldom exceeding half an inch in height ; erect-ovate, becoming more elongate proportionally with increased growth. Valves slightly convex. Hinge short, from half to two-thirds as long as the width of the body of the shell, strongly and distinctly aurieu- lated. Beaks of the valves small and pointed, and the cardinal slopes long, straight or slightly concave, extending to near the point of greatest width of the body of the shell. Left valve smooth or but faintly marked by fine concentric lines, and a few (five or six) very faint radii. Ears smaller than in the opposite valve, both sloping toward the beak on the outer mar- gin. Right valve marked with crowded concentric folds or elevated lines ; also by five or six radiating lines ; not always present. On most specimens there are distinctly rounded concentric folds or varices, but on some they are thin, sharp lines; always more crowded and usually finer toward the front, in adult specimens. Ears very distinct; that of the posterior side sloping toward the beak and the anterior one rounded at the extremity and deeply notched.
" This shell is very closely allied to P. simplicus Conrad, but differs in being more elevated and in the surface markings, that one being generally smooth or imperceptibly marked. In making these comparisons I have used a number of each valve of the present species from New Jersey, and a fine series of A. simplicum from the typical locality, Eufaula, Alabama, and it leaves no doubt in my mind as to their complete specific distinction." —Whitfield, 1886.
Type Locality. — Haddonfield, New Jersey.
A single valve from the Matawan of Anne Arundel County has been rather dubiously referred to this species because of the size and general outline and the faint traces of a concentric sculpture.
Occurrence. — MATAWAN FORMATION. Ulmstead Point, Anne Arundel County.
MARYLAND GEOLOGICAL SURVEY 595
Collections. — Maryland Geological Survey, Philadelphia Academy of Natural Sciences, New Jersey Geological Survey.
Outside Distribution. — Matawan Formation. Merchantville clay marl and \\yoodbury clay, New Jersey. Monmouth Formation. Navesink marl (rare), New Jersey.
PECTEX SIMPLICIUS Conrad Plate XXXIV, Figs. 8, 9
Pecten simplicius Conrad, 1860, Jour. Acad. Nat. Sci., Phila., 2d ser, vol. iv,
p. 283, pi. xlvi, fig. 44. Sincyclonema f simplicus Meek, 1864, Check List Inv. Fossils, N. A., Cret.
and Jur., p. 7.
Pecten simplicus Conrad, 1868, Cook's Geol. of New Jersey, p. 725. Sincyclonema simplicus Gabb, 1876, Proc. Acad. Nat. Sci., Phila., p. 319. Amusium simplicum Whitfield, 1885, Mon. U. S. Geol. Survey, vol. ix, p. 51,
pi. vii, figs. 11, 12. Pecten simplicius Weller, 1907, Geol. Survey of New Jersey, Pal., vol. iv,
p. 480, pi. li, fig. 6.
Description. — " Ovate, thin, smooth and shining; ears moderate, nearly equal ; both valves slightly convex ; the upper valve slightly tumid on the umbo ; inner margin minutely crenulated." — Conrad, 1860.
Type Locality. — Eufaula, Alabama, or Tippah County, Mississippi.
Shell small, smooth, lustrous, moderately compressed, the left valve a little more so than the right ; anterior and posterior lateral margins con- verging at an angle of from 70° to 90°, base broadly and evenly arcuate; hinge-line straight, a little less than half the latitude of the shell, auricles small, trigonal, the anterior slightly larger than the posterior and sinuated in the right valve to accommodate the bvssus ; sinuses between the auricles
O i/
and the disk clearly defined; external surface highly polished, smooth excepting for faint incremental striations and an occasional microscopi- cally fine radial shagreening ; characters of the interior unknown.
This Pecten, in spite of its small dimensions, is a conspicuous factor in the Cretaceous marls of Maryland by reason of its wide distribution and its shining surface. This shell is so thin and flaky, however, that for all it is so common it has not been possible to separate any one of the forms from its matrix.
596 SYSTEMATIC PALEONTOLOGY
P. simplicius Conrad has been confused in the synonymies with P. con- radi Whitfield, a slightly larger shell which is characterized by the develop- ment of sharp, elevated, concentric lamellae, approximately fifteen in number. The typical forms of the two species are conspicuously distinct but some of the peripheral members are difficult to separate.
Occurrence. — M ATA WAN FORMATION. Ulmstead Point, Anne Arundel County. MONMOUTH FORMATION. Brightseat, Brooks estate near Seat Pleasant, Friendly, 1 mile west of Friendly, and McNeys Corners, Prince George's County.
Collections. — Maryland Geological Survey, New Jersey Geological Sur- vey, U. S. National Museum.
Outside Distribution. — Monmouth Formation. Eed Bank sand and Tinton beds, New Jersey. Black Creek Formation. North and South Carolina. Peedee Sand. North and South Carolina. Eutaw Formation (Tombigbee sand member). Exogyra ponderosa zone, Mortoniceras sub- zone, Georgia. Ripley Formation. Exogyra ponderosa zone, Union Springs, Alabama. Exogyra costata zone, Georgia; Eufaula, Alabama. Extreme top of zone, Pataula Creek, Georgia ; Chattahoochee River, Ala- bama; Lowndes County, Mississippi.
PECTEN QUINQUECOSTATUS Sowerby Plate XXXIV, Fig. 10
Pecten quinqueco status Sowerby, 1814, Min. Conch., vol. i, p. 122, pi. Ivi,
figs. 4-8.
Pecten versicostatus Lamarck, 1819, Anim. sans Vert., vol. vi, p. 181. Pecten quinquecostatus Brongniart, 1822, Geol. des Env. Paris, pi. iv, fig. 1. Pecten quinquecostatus Nilsson, 1827, Petrif. Suecana, p. 19, tab. ix, fig. 8;
tab. x, fig. 7. Pecten quinquecostatus Morton, 1830, Am. Jour. Sci., 1st ser., vol. xvii, p.
285; vol. xviii, pi. iii, fig. 5.
Pecten versicostatus Deshayes, 1832, Enc. Meth., t. 3, p. 727. Pecten quinquecostatus Morton, 1834, Syn. Org. Rem. Cret. Group U. S., p.
57, pi. xix, fig. 1.
Pecten quinquecostatus Goldfuss, 1836, Petrif. Germ., t. 93, fig. 1. Pecten quinquecostatus Bronn, 1838, Lethsea Geogn., Bd. ii, pp. 678-680, taf.
xxx, fig. 17. Janira quinquecostata d'Orbigny, 1846, Paleont. Franc. Terr. Cret, vol. iii,
p. 632, pi. ccccxliv, figs. 1-5.
597
Janira mortoni d'Orbigny, 1850, Prod. Paleont. Strat, vol. ii, p. 253. Pecten quadricostatus var. Roemer, 1852, Kreide. von Texas, p. 64, pi. viii,
figs. 4a-4c. Pecten quadricostatus Shumard, 1854, Marcy, Expl. Red River, Louisiana,
p. 178, pi. ii, figs. 2a, 2b; pi. iii, fig. 6.
Neithea mortoni Gabb, 1862, Proc. Acad. Nat. Sci., Phila. for 1861, p. 365. Neithea mortoni Meek, 1864, Check List Inv. Fossils N. A., Cret. and Jur.,
p. 7.
Neithea mortoni Conrad, 1868, Cook's Geol. of New Jersey, p. 725. Pecten quadricostatus Credner, 1870, Zeitsch. deutsch. geol. Gesell., Bd.
xxii, p. 232. Vola quinquecostata Stoliczka, 1871, Mem. Geol. Survey India, Palaeont. In-
dica. Cret. Faunas of Southern India, vol. iii, p. 437, pi. xxxi, figs. 1-6;
pi. xxxviii, figs. 4-9. Neithea quinquecostata Whitfield, 1885, Mon. U. S. Geol. Survey, vol. ix, p.
56, pi. viii, figs. 12-14. Neithea quinquecostata Weller, 1907, Geol. Survey of New Jersey, Pal., vol.
iv, p. 481, pi. Ii, figs. 7-12. Vola quinquecostata Bose, 1910, Bol. Inst. Geol. Mexico, p. 99, pi. xv, figs.
19, 20.
Description. — " Subtriangular, rather oblique, front semicircular, toothed ; convex valves gibbous, ribbed, principal costa six, with four lesser ones between each ; surface finely transversely striated. Upper valve flat- toothed. The obliquity of this shell is slight, the length not much greater than the width ; the lines of growth frequently being deep and crossed by the ribs give the shell a fringed or furbellowed aspect ; the flat valve has diverging striae and notches corresponding in number with the costs upon the hollow valve. The whole surface is covered with minute transverse stria?, which in the chalk specimens are often nearly obliterated. Figs. 4 and 5 are from the Sussex chalk near Lewes, by favor of G. A. Mantell, Esq. ; they very much accord with those of the green sand from Wiltshire, figured below, but appear to be longer, and to have the transverse striae of growth very remarkable. The shell represented at fig. 5 is a curiosity, showing the inner side of the flat valve, which is slightly convex within. I gathered the small shell, fig. 6, at Chute farm, it is a young deep under- valve, with the transverse striae of growth neatly arching between the larger six coste. Figs. 7 and 8 show the upper and under valves of different specimens, they are from the green sand at Chute, and are chiefly siliceous ; for the use of one I am indebted to Thomas Meade, Esq. Such are said
598 SYSTEMATIC PALEONTOLOGY
to be found at Devizes and Blackdown, with the upper valve. It is pos- sible that these are different species from those in the Chalk, the costae are less prominent, and the stria? more distinct; at present, however, I can consider them only as varieties. Tab. 56, fig. 3, represents a specimen in ferruginous sandstone from Chute, which may possibly prove to be a dis- tinct species. Its length exceeds its breadth by one-fifth, and on the sides of the larger costae are two lesser ones, which are partly blended with them ; the surface is nearly smooth. I have only seen this specimen." — Sowerby, 1812.
Shell rather large for a Cretaceous Pecten; cordate, very strongly inequi- valve, subequilateral, lower valve highly convex, the upper flattened or feebly concave ; maximum diameter at or a little behind the median hori- zontal; umbone of right valve very prominent, evenly inflated, rising well above the hinge line, orthogyrate ; dorsal margins diverging at an angle of approximately 90°, produced so that the ventral and lateral margins subscribe an arc of only about 180° ; external surface of lower valve sculp- tured with five or rarely six elevated, evenly rounded primaries, subequal in size and spacing and between each pair three or four more or less equal secondaries; submargins sculptured with rather fine close-set radials fi.ve in number, as a rule ; ornamentation of upper valve more uniform in char- acter, usually of twenty to twenty-five subequal and equispaced, well rounded and elevated radials ; incremental sculpture fine and sharp ; hinge line rather short, not far from five-ninths of the maximum latitude, over- hung by the umbo of the right valve ; auricles only slightly unequal, the anterior a little more produced and relatively lower and less strongly lirate than the posterior ; posterior auricle receding below the hinge line, the anterior feebly constricted to form the byssal notch ; characters of interior of shell not known.
The identity of the American species with the European has been ques- tioned since the day of d'Orbigny. The Maryland representation is very meager and offers very little assistance toward the solution of the problem. As in Pycnodonte vesicularis the true affinities of the group should be worked out once for all by an exhaustive study of material from all the representative localities. If the two forms prove distinct Sowerby's name
MARYLAND GEOLOGICAL SURVEY 599
must be retained for the European fossil and d'Orbigny's mortoni sub- stituted for the American. It is the personal conviction of the writer that the two forms are identical, or at least that they cannot be separated on a geographical basis. D'Orbigny's criterion certainly will not stand, i. e., that the American form differs from the European in the presence of five instead of four secondaries between each pair of primaries. The normal number in the American form is four as it is in the European and South Indian, but as in the foreign types this number is occasionally increased to five or reduced to three. The outline and relative proportions vary within rather narrow limits throughout the occurrence, and though there is a suspicion that the maximum diameter may fall a little nearer the median horizontal in the American individuals, this cannot be veri-' fied Avithout the examination of much more material than is available at present.
Occurrence. — MAGOTHY FORMATION. Good Hope Hill, District of Columbia. MATAWAN FORMATION. Post 236, Camp Fox, Chesapeake and Delaware Canal, Post 192, Camp U & I, Chesapeake and Delaware Canal, Delaware. MONMOUTH FORMATION. Two miles west of Dela- ware City on John Higgins farm, Delaware; ? Fredericktown, Cecil County; Waterbury, Anne Arundel County, Maryland. KANCOCAS FOR- MATION. ? NoxontoAvn Pond, Delaware.
Collection*. — Maryland Geological Survey, New Jersey Geological Survey, U. S. National Museum, Geological Survey of India.
Outside Distribution. — Matawan Formation. Merchantville clay marl, Marshalltown clay marl, New Jersey. Monmouth Formation. Navesink marl, New Jersey. Eutaw Formation (Tombigbee sand member). Exo- gyra ponderosa zone, Mortoniceras subzone, Georgia; Russell County, Warrior River and Tombigbee River, Alabama; Tombigbee River, Mis- sissippi. Eipley Formation. Exogyra costata zone, Georgia; Chatta- hoochee River, Alabama ; Wilcox, Pontotoc and ChickasaAv counties, Mis- sissippi. Selma Formation. Exogyra ponderosa zone, Monroe and Prentiss counties, Mississippi; Tennessee. Exogyra costata zone, Tom- bigbee River, Alabama: east-central Mississippi; Lee, Clay and Alcorn counties, Mississippi. Cenomanian. ? Mexico, and England. Turanian.
600 SYSTEMATIC PALEONTOLOGY
Central Europe. Senonian. Central Europe. Ootatoor Formation. Southern India. Tricliinopoli Formation. Southern India. Arrialoor Formation. Southern India.
Family LIMIDAE
Genus LIMA (Bruguiere) Cuvier [Tableau 616mentaire d'histoire naturelle, 1798, p. 421]
Type. — Ostrea lima Linne.
Shell auriculate, auricles unequal ; outline usually ovate, scoop-shaped and obliquely truncated laterally; valves closed inferiorly but gaping anteriorly and sometimes posteriorly ; exterior surface rarely smooth, gen- erally sculptured with simple or imbricated radial striae ; umbones rather prominent and distant ; hinge edentulous ; ligament internal, lodged in a subumbonal pit ; pallial line simple ; single muscular scar excentric, nearer to the posterior than the anterior margin.
A genus indicated in the Carboniferous, culminating in the Cretaceous and sparsely represented in nearly all the recent seas by white or colorless shells, which may be attached by a byssus or may swim freely with a motion similar to that of Pecten.
A. Both anterior and posterior auricles developed.
1. Radial sculpture overridden by the concentric on the medial por-
tion of the shell Lima reticulata
2. Concentric sculpture obsolete upon the medial portion of the shell.
Lima serrata
B. Posterior auricle obsolete, anterior auricle very large Lima obliqua
LIMA RETICULATA Forbes Plate XXXIV, Figs. 12, 13
Lima reticulata Forbes, 1845, Quart. Jour. Geol. Soc., London, vol. i, p. 62;
two text figures. Lima reticulata Meek, 1864, Check List Inv. Fossils, N. A., Cret. and Jur.,
p. 7.
Radula reticulata Conrad, 1868, Cook's Geol. of New Jersey, p. 725. Radula reticulata Stoliczka, 1871, Mon. Geol. Survey of India, Palaeont. In-
dica., Cret. Fauna Southern India, vol. iii, p. 416.
Etymology: Lima, a file — a name suggested, doubtless, by the rasping ex- terior surface.
MARYLAND GEOLOGICAL SURVEY 601
Radula reticulata Whitfleld, 1885, Mon. U. S. Geol. Survey, vol. ix, p. 63,
pi. ix, figs. 8, 9. (Synonymy excluded.) Lima reticulata Weller, 1907, Geol. Survey of New Jersey, Pal., vol. iv, p.
492, pi. liv, figs. 3, 4.
Description. — "L. testa ovata, obliqua, inflata, tenui, longitudinaliter sulcata, sulcis reticulatis, numerosis. Habitat, Nov. Jersey." — Forbes, 1845.
" Shell small, moderately oblique, strongly ovate, and inflated. Hinge short; beaks proportionally strong, and projecting beyond the cardinal line. Valves nearly equal ; anterior margin straight, and not at all gaping ; auriculations small but distinct, rectangular or very slightly pointed at their outer angles. Surface radiately ribbed, those of the anterior and posterior slopes faintly marked or obsolete, ribs (about thirty) distinct, with live or more indistinct on each side; subangular on the middle of the valves and rounded toward the sides, crenulate or subspinose on the larger specimens when well preserved, but often appearing nearly smooth. Entire surface marked by concentric lines which give a roughened surface when perfect, giving the reticulated character indicated by the specific name. The shells are all small, seldom exceeding three-fourths of an inch in length, and are very fragile. The right valve apears to be a little less ventricose and the beak shorter than the left in all the specimens which I have seen where the two are united." — Whitfield, 1885.
There is apparently a large amount of variation in this small species, and, as the type is not in this country, it is difficult to determine its proper limits. In Maryland the forms referred to this group are all young and of rather doubtful affinities, so that they throw no light upon the characters of the race. Radula denticulicosta Gabb is probably distinct if Gabb was correct in his observation that " at both the anterior and posterior sides the ribs disappear for about one-sixth the width of the shell."
Occurrence. — MONMOUTH FORMATION. Brightseat and McNeys Cor- ners, Prince George's County.
Collections. — Maryland Geological Survey, New Jersey Geological Sur- vey, U. S. National Museum.
602 SYSTEMATIC PALEONTOLOGY
Outside Distribution. — Mataivan Formation. Merchantville clay marl, Woodbury clay, Marshalltown clay marl, Wenonah sand, Xew Jersey. Monmouth Formation. Navesink marl, New Jersey. Black Creel- for- mation. North and South Carolina. Peedee Sand. North and South Carolina. Eutaiv Formation (Tombigbee sand member). Exogyra i>on- derosa zone, Mortoniceras subzone, Georgia; Russell County, Alabama. Eipley Formation. Exogyra ponderosa zone, Union Springs. Alabama; Booneville, Mississippi. Exogyra costata zone, Georgia; Eufaula, Ala- bama ; east-central Mississippi ; Alcorn, Union and Tippah counties, Mis- sissippi. Selma Chalk. Exogyra costata zone, east-central Mississippi. Extreme top of zone, Pataula Creek, Georgia.
LIMA SERRATA n. sp. Plate XXXIV, Figs. 14, 15
Description. — Shell small, moderately inflated, ovate in outline, inequi- lateral; anterior area obtusely angulated; posterior evenly rounded: base line arcuate, somewhat obliquely produced in front; umbones moderately gibbous orthogyrate, slightly posterior in position : external surface sculp- tured with thirty-two primary costa? (in the unique type the summits are acutely angulated and form with the ' more obtuse interradials a sharply serrate profile) ; radials upon the posterior portion less angular; the ten anterior costae rounded, over-run and minutely nodulated by the incrementals ; minute secondary threadlets developed in the interspaces on the posterior medial portion of the disk; posterior submargin devoid of radial sculpture; incremental sculpture obsolete over the medial portion of the shell and only feebly developed posteriorly; submargins not impressed, auricles minute, the anterior more so than the posterior, tri- gonal, their dorsal margins forming the straight hinge margin (unfor- tunately the posterior auricle was lost in shipment to the artist) ; ligament internal, lodged in a small but relatively very wide resilium directly beneath the umbones ; hinge dentition not developed ; shell monomyarian, .the single muscle scar subcircular, placed above and behind the medial planes of the shell ; pallial line indistinct ; interior finely plicated even to the umbonal region in harmony with the external ribbing.
MARYLAND GEOLOGICAL SURVEY 603
Dimensions. — Altitude 8 mm, latitude 7.75 mm., semi-diameter, 2 mm.
Type Locality. — Brightseat, Prince George's County.
This species differs from its near relative, L. reticulata Lyell and Forbes, in the somewhat smaller size, the much more angular costse, the absence of any trace of concentric sculpture upon the medial portion of the disk and the development of occasional secondaries.
Occurrence. — MONMOUTH FORMATION. Brightseat and MclSTeys Cor- ners, Prince George's County.
Collection. — Maryland Geological Survey.
LIMA OBLIQUA n. sp. Plate XXXIV, Fig. 11
Description. — Shell of moderate size for the group, very thin and fragile, inequilateral, ovate in outline, obliquely produced along the diagonal from the umbones to the anterior ventral margin ; posterior por- tion of the shell compressed and obtusely rounded at the junction of the dorsal lateral and the lateral ventral margins ; maximum inflation in the umbonal region and along the dorsal half of the diagonal ; umbones acute, obliquely compressed, somewhat posterior in position; posterior auricle obsolete, the anterior very large, fully one-third as wide as the entire .shell, its submargin deeply impressed and sharply differentiated from the disk ; external surface sculptured with some twenty-six low, flattened radial costse which tend to diastomose posteriorly; intercalations occasionally developed near the ventral margin ; intercostal areas shallow, not quite so wide as the costals, radial sculpture absent upon the auricle, excepting for two or three very faint threadlets upon the extreme posterior portion; concentric sculpture absent, excepting for very faint striations upon the disk ; byssal sinus probably very shallow ; characters of hinge and interior not known ; ventral margin minutely crenated by the ribbing.
Dimensions. — Altitude 11 mm., latitude 8.5 mm., semi-diameter 2.5 mm.
This species is described from two imperfect specimens, but the char- acters preserved are so peculiar and so diagnostic that the form lias
40
604 SYSTEMATIC PALEONTOLOGY
seemed worthy of a name. The species differs from the other East Coast forms in the obliquely produced and rather depressed outline, the low flattened posteriorly dichotomoug riblets, the very large sharply differ- entiated anterior ear and the absence of the posterior auricle.
Occurrence. — MONMOUTH FOKMATIOX. Brooks estate near Seat Pleas- ant, Prince George's County.
Collection. — Maryland Geological Survey.
Superfamily ANOMIACEA Family ANOM1IDAE
Genus PARANOMIA Conrad [Jour. Acad. Nat. Sci., Phila., vol. iv, 1860, p. 290]
Type. — Placunanomia saffordi Conrad.
" Inequivalve, irregular ; larger valve radiate, spinous or subspinous ; lower valve flat or concave; hinge very thin and fragile, having a longi- tudinal flat shelly plate extending from the apex; hinge of upper valve plain, entire, extremely thin. 1 have often found fragments of this singu- lar genus in the New Jersey Cretaceous beds, but never saw the hinge before Mr. Safford's specimens were received from Tennessee. The muscular impression is not visible on any of the many valves I have seen." —Conrad, 1860.
" In 1867 Conrad described a genus Paranomia, from the Ripley group (Upper Cretaceous) of Alabama, to which he referred his Placunanomia saffordi (Journ. Acad. Nat. Sci., 2d ser., iv, p. 290, pi. 46, fig. 21) and the Placuna scabra of Morton. The typical species is ill preserved, and the beaks almost always wanting, but, from the examination of a large number of specimens, it seems probable that the genus resembles Monia in its external characters; the presence of a triangular chondrophore recalls Anomia, but there is not sufficient evidence of a permanent foramen, the musclar impressions are not preserved, and there is in the right valve, asso- ciated with the single chondrophore, a pair of low, narrow crests, recalling
Etymology: ^apd near, anomia.
MARYLAND GEOLOGICAL SURVEY 605
those of Placenta, but obviously of different function. The genus is a puzzle and cannot as yet be safely united with any other." — Dall,1 1898.
A. Outline circular; radials relatively fine and crowded. . . .Paranomia scabra
B. Outline ovate; radials relatively coarse and distant Paranomia lineata
PARAXOMIA SCABRA (Morton) Conrad
Placuna scabra Morton, 1834, Syn. Org. Rem. Cret. Group U. S., p. 62. Placunomia scabra Meek, 1864, Check List Inv. Fossils, N. A., Cret. and
Jur., p. 6.
Paranomia scabra Conrad, 1867, Am. Jour. Conch., vol. iii, p. 8. Paranomia scabra Conrad, 1868, Cook's Geol. of New Jersey, p. 724. Paranomia scabra Whitfield, 1885, Mon. U. S. Geol. Survey, vol. ix, p. 44,
pi. x, fig. 10.
Paranomia scabra Johnson, 1905, Proc. Acad. Nat. Sci., Phila., p. 12. Paranomia scabra Weller, 1907, Geol. Survey of New Jersey, Pal., vol. iv,
p. 500, pi. Iii, figs. 10-13 (ex parte).
Description. — " With numerous beaded costse, radiating from the hinge to the margin; shell thin, suborbicular, compressed. From one inch to three inches in diameter." — Morton, 183-1.
Type Locality. — New Jersey.
The type specimen figured by Whitfield in 1885 is a mere frag- ment which, as that eminent New Jersey paleontologist has observed, is " scarcely sufficient for generic identification." However, its reference to Paranomia is probably justified. The species as delimited by the aid of later collections is thin, flattened and subcircular in outline, sculptured externally with approximately thirty rather fine radials which occasionally diastomose and which are quite sharply spinose toward the ventral margin. The intercostal areas are narrow, scarcely or not at all exceeding the costals in width. The incremental sculpture is quite vigorous and suffi- cient to imbricate the radial.
Paranomia saffordi Conrad from Tennessee and the type of the genus develop apparently a much more regular and rather coarser and more dis- tant radial sculpture. Paranomia lineata Conrad runs smaller, is ovate rather than subcircular and has fewer, more prominent and more widely spaced radials. Although it is not impossible that a connecting series may
1 Trans. Wagner Free Inst. Sci., Phila,, vol. iii, pt. iv, p. 773.
606 SYSTEMATIC PALEONTOLOGY
later be established which will include either or both P. saffordi and P. lineata, there does not seem at present to be sufficient evidence.
Occurrence. — MATAWAIST FORMATION. Opposite Post 198, Chesapeake and Delaware Canal. Delaware.
Collections. — Maryland Geological Survey, Philadelphia Academy of Natural Sciences, New Jersey Geological Survey, U. S. National Museum.
Outside Distribution. — Matawan Formation. Merchantville clay marl, Marshalltown clay marl, New Jersey. Peedee Sand. North and South Carolina. Eutaw Formation (Tombigbee sand member). Exogyra pon- derosa zone, Alcorn County, Mississippi. Ripley Formation. Exogyra cos- tata zone, Georgia ; Euf aula, Alabama ; east-central Mississippi ; Pontotoc County, Mississippi. Selma Chalk. Exogyra ponderosa zone, Warrior Eiver, Alabama ; Monroe and Chickasaw counties, Mississippi. Exogyra costata zone, Tombigbee Eiver and Sumter County, Alabama ; east-central Mississippi ; Chickasaw, Pontotoc and Alcorn counties, Mississippi.
PARANOMIA LINEATA Conrad Plate XXXV, Figs. 11, 12
Placunanomia lineata Conrad, 1860, Jour. Acad. Nat. Sci., Phila., 2 ser.,
vol. iv, p. 291, pi. xlvi, fig. 20. Placunomia lineata Meek, 1864, Check List Inv. Fossils, N. A., Cret. and
Jur., p. 6.
Paranomia lineata Conrad, 1867, Am. Jour. Conch., vol. iii, p. 8. Paranomia lineata Whitfield, 1885, Mon. U. S. Geol. Survey, vol. ix, p. 45,
pi. ix, fig. 10.
Paranomia lineata Johnson, 1905, Proc. Acad. Nat. Sci., Phila., p. 12. Paranomia scabra Weller, 1907, Geol. Survey of New Jersey, Pal., vol. iv,
p. 500, pi. Iii, figs. 10-13 (ex parte).
Description. — " Subovate, thin, much compressed, irregular ; lower valve concave, obsoletely radiate; near the summit is a resemblance to a triangular plate inserted in the shell with a raised margin ; this portion is longitudinally minutely striate and resembles one of the opercular valves of a Balanus; upper valve convex, lobed or twisted; radiated with about thirty rugose, slightly raised, subaculeated lines; surface rugose." - Conrad, 1860.
Type Locality. — Tennessee.
MARYLAND GEOLOGICAL SURVEY 607
Paranomia lineata Conrad is separated from P. scabra (Morton) Con- rad by the regularly ovate outline and its coarser, more prominent and more distant radials. All of the specimens observed have been a little smaller than the adult P. scabra, but this may have been due only to the fortunes of collecting.
Occurrence. — MATAWAN FORMATION. One mile east of the Maryland- Delaware Line, Chesapeake and Delaware Canal, Delaware.
Collections. Maryland Geological Survey, Philadelphia Academy of Natural Sciences, New Jersey Geological Survey, U. S. National Museum.
Outside Distribution. — Monmouth Formation. Navesink marl, New Jersey. ? Ripley Formation. Tennessee.
Genus ANOMIA (Linne) Miiller [Prodr. Zool. Dan., 1776, pp. xxxi, 248]
Type. — Anomia ephippium Linne.
Shell inequivalve, adherent, generally subcircular or oblong; left valve more or less convex, right valve flattened ; hinge margin of left valve often incurved and slightly thickened; ligament scar found directly beneath left umbone ; interior of disk of left valve scarred with an adductor and a major and minor byssal impression, the major byssal scar being the largest of the three and dorsal to the adductor and minor byssal scars which are usually subequal; interior of right valve containing foraminal opening and, ventral to it, the impression of the adductor muscle ; posterior dorsal margin of right valve carrying inconspicuous ligamental process ; pallial line simple.
" The fossil species of this group are very difficult things to study, since the lower valve is seldom preserved and the muscular impressions can seldom be made out. . . . To the natural difficulties is added that due to the fact that the sculpture in this genus is very variable in perfectly normal specimens and is further complicated by the differences of form and sur- face, due to the object upon which they are sessile. I have satisfied myself by the examination of a large number of recent specimens belonging to a single species from a single locality that the relative positions of the
Etymology: dvoyueuos unequal, unlike.
608 SYSTEMATIC PALEONTOLOGY
adductor and byssal scars of the left valve are not constant in the same individual at all ages, and consequently that small differences of this kind cannot safely be used as specific distinctions. The best character seems to be the more minute surface sculpture when fully developed in normal specimens." — Dall, 1898.1
Ancestral forms of this genus have been recognized in rocks as ancient as the Devonian. The recent species number about forty and are widely di- tributed along the shores from low-water to one hundred fathoms.
A. External surface not radially plicate.
1. Outline sub-circular; concentric lamination, very close excepting
in the umbonal region Anomia argentaria
2. Outline transversely ovate; concentric lamination rather distant.
Anomia tellinoides
B. External surface radially plicate.
1. Radial sculpture, lirate rather than cordate, primaries and second-
aries not conspicuously differentiated Anomia ornata
2. Radial sculpture cordate rather than lirate; primaries and second-
aries conspicuously differentiated Anomia forteplicata
ANOMIA AKGEXTARIA Morton Plate XXXV, Figs. 1, 2
Anomia argentaria Morton, 1833, Am. Jour. Sci., 1st ser., vol. xxiii, p.
293, pi. v, fig. 10. Anomia argentaria Morton, 1834, Syn. Org. Rem. Cret. Group, U. S., p. 61,
pi. v, fig. 10. Anomia argentaria Meek, 1864, Check List Inv. Fossils, N. A., Cret. and
Jur., p. 6. Anomia argentaria Conrad, 1868, Cook's Geol. Survey of New Jersey, p.
724.
Anomia argentaria Conrad, 1875, Kerr's Geol. of North Carolina, Appen- dix A, p. 13.
Anomia argentaria Gabb, 1876, Proc. Acad. Nat. Sci., Phila., p. 319. Anomia argentaria Whitfield, 1885, Mon. U. S. Geol. Survey, vol. ix, p. 42,
pi. iv, figs. 10, 11 (fig. 9 excluded).
Anomia argentaria Johnson, 1905, Proc. Acad. Nat. Sci., Phila., p. 12. f Anomia argentaria Bose, 1906, Bol. Inst. Geol. Mexico, No. 24, p. 38, pi. i,
fig. 8. Anomia argentaria Weller, 1907, Geol. Survey of New Jersey, Pal., vol. iv,
p. 496, pi. liv, figs. 11-15. ? " Anomia subtruncata " Bose, 1913, Bol. Inst. Geol. Mexico, No. 30, p. 41,
pi. v, fig. 1.
Description. — " Thin, round, with numerous concentric strige."- Morton, 1833.
1 Trans. Wagner Free Inst. Sci., Phila., vol. iii, pt. iv, p. 781.
MARYLAND GEOLOGICAL SURVEY 609
Type Locality. — New Jersey.
Shell subcircular or irregular in outline with a silvery sheen both within and without, thin but tough, of moderate size, the adults from 15 to 30 mm. in circumference ; left valve usually convex, though varying widely in the degree of convexity; right valve, through which the byssus is extruded, flattened; umbones central, almost marginal, very inconspicu- ous, scarcely interrupting the regular outline of the valve ; external sur- face ornamented with thin, concentric overlapping lamellae which are frequently radially lineated ; ligament submarginal, attached beneath the umbo of the left valve ; hinge edentulous ; interior scarred with a large, major byssal impression, medial in position and quite high up under the umbones and ventral to it, the minor byssal impression, and the posterior muscle adductor ; a third byssal scar of minute size underneath the dorsal margin, a little in front of the umbones ; inner ventral margins simple.
This species is one of the most abundant bivalves in the Upper Cre- taceous faunas of Maryland. For all the shell is so thin, it is very tena- cious and easily separable from the matrix. It is an unusually well char- acterized species and even the fragments can be determined with assurance by the silvery sheen, the crowded concentric laminae and in the majority of individuals by the fine, radial lineation.
The form varies to a certain extent, as do all members of this variable genus, in the outline, the degree of compression of the valves, and par- ticularly in the development of the radial sculpture. However, limits must be placed even for variable species and it is not probable that they should be made wide enough to include A. tellinoides Conrad, which is constant in its transversely ovate outline, lack of lustre, rather distant concentric lamination and absence of radial striations.
Some puzzling little forms from the Monmouth at Brightseat are closely related genetically with the A. argentaria Morton. They are apparently young, frequently ovate, rather thin, circular in outline and are sculptured with a few wide, sharp-edged concentric frills which are often radially lineated. Concentric lamina? so distantly spaced and so sharply frilled have not been observed among the A. argentaria.
610 SYSTEMATIC PALEONTOLOGY
Occurrence. — MATAWAN FORMATION. Post 198, Chesapeake and Dela- ware Canal, Delaware; head of Atagothy Eiver, Gibson's Island, Anne Arundel County, Maryland. MONMOUTH FORMATION. Two miles west of Delaware City on John Higgins farm, Delaware; mouth of Turner's Creek, Kent County; Brightseat, railroad cut west of Seat Pleasant, Brooks estate near Seat Pleasant, Friendly, and 1 mile west of Friendly, Prince George's County, Maryland. RANCOCAS FORMATION ( ?). Noxon- town Pond, Delaware.
Collections. — Maryland Geological Survey, Philadelphia Academy of Natural Sciences, New Jersey Geological Survey, U. S. National Museum.
Outside Distribution. — Magothy Formation. Cliffwood clay, New Jersey. Matawan Formation. Merchantville clay marl, Woodbury clay, Marshalltown clay marl and Wenonah sand, New Jersey. Monmouth Formation. Navesink marl and Red Bank sand, New Jersey. Black Creek Formation. North and South Carolina. Peedee Sand. North and South Carolina. Eutaw Formation (Tombigbee sand member). Exo- gyra ponderosa zone, Mortoniceras subzone, Georgia; Russell and Dallas counties, Alabama ; Tombigbee River, Clay County, Mississippi. Exogyra ponderosa zone, Alcorn County, Mississippi; Georgia; Union Springs and Russell County, Alabama. Exogyra costata zone, Geor- gia; Chattahoochee River and Eufaula, Alabama; east-central Mis- sissippi ; Lee, Pontotoc, Chickasaw, Union and Tippah counties, Missis- sippi. Selma Chalk. Exogyra ponderosa zone, Elmore County, Alabama ; Clay, Monroe, Alcorn and ? Prentiss counties, Mississippi. Exogyra cos- tata zone, Wilcox and Sumter counties, Alabama ; east-central Mississippi ; Chickasaw, Lee, Clay, Alcorn and Prentiss counties, Mississippi. Extreme top of zone, Pataula Creek, Georgia; Lowndes County, Mississippi. Senonian. Mexico.
ANOMIA TELLINOIDES Morton Plate XXXV, Figs. 3, 4
Anomia tellinoides Morton, 1833, Am. Jour. Sci., 1st ser., vol. xxiii, p. 294,
pi. v. fig. 10. Anomia tellinoides Morton, 1834, Syn. Org. Rem. Cret. Group, U. S., p. 61,
pi. v, fig. 11.
MARYLAND GEOLOGICAL SURVEY 611
Anomia tellinoides Meek, 1864, Check List Inv. Fossils, N. A., Cret. and
Cret. and Jur., p. 7.
Anomia tellinoides Conrad, 1868, Cook's Geol. of New Jersey, p. 724. Anomia tellinoides Whitfield, 1885, Mon. U. S. Geol. Survey, vol. ix, p. 43. Anomia tellinoides Johnson, 1905, Proc. Acad. Nat. Sci., Phila., p. 12. Anomia argentaria Weller, 1907, Geol. Survey of New Jersey, Pal., vol. iv,
p. 496 (ex parte, description and figures excluded).
Description. — " Irregular, but mostly subovate, with concentric undu- lations. Both these species are common in New Jersey; the latter resembles A. ephippium, to which it is referred in the first part of this Synopsis."— Morton, 1833.
Type Locality. — New Jersey.
Shell rather thin but tenacious, inequilateral, transversely ellipsoidal in outline, the lower valve moderately convex; anterior portion of the shell constricted in front of the umbones ; anterior margin broadly and evenly rounded ; posterior portion of shell symmetrical, rounded ; base arcuate ; umbones low, not very conspicuous, with ill-defined apices placed as a rule a little behind the median line ; external surface sculptured with an indistinct and rather distant concentric lamination; ligament submar- ginal attached beneath the umbo of the left valve; hinge plate not developed, edentulous; pedal and byssal scars indistinct.
This species has been confused in the synonymies with A. argentaria. The forms are certainly closely related but there is not sufficient evidence of their identity. A. tellinoides is transversely ovate in outline, rather than subcircular, the surface is less silvery, the concentric lamination less crowded and the radial striations much less commonly developed than in the more prolific A. argentaria.
Occurrence. — MONMOUTH FORMATION. Briar Point, Chesapeake and Delaware Canal, Delaware.
Collections. — Maryland Geological Survey, Philadelphia Academy of Natural Sciences, New Jersey Geological Survey.
Outside Distribution. — Monmoutli Formation. Navesink marl, New Jersey.
612 SYSTEMATIC PALEONTOLOGY
ANOMIA ORNATA Gabb Plate XXXV, Figs. 5, 6
Anomia argentaria var. ornata Gabb, 1876, Proc. Acad. Nat. Sci., Phila., p.
320. "Anomia argentaria (Gabb) " Boyle, 1893, Bull. U. S. Geol. Survey, No.
102, p. 44.
Description. — " Accompanying these is another form, represented by no less than fifteen specimens agreeing well with one another. Unlike the typical A. argentaria, they are ornamented by a uniform pattern, clearly not the impression of a surface to which they were attached. In form and size they do not differ from .4. argentaria, but the ornament is a series of radiating ribs, one set large, flattened on top, and well defined; between these are interpolated from one to three smaller ribs. In most cases this alternation is well defined ; though in two or three the large ribs are nearer in size to the small ones. On the typical argentaria this radiation is never observed, even in a rudimentary manner, and on some of my specimens it begins at the very apex ; but on several the first half inch in diameter, or less, of the shell does not differ from argentaria, while after that the ribs begin, first on thread-like lines, finally developing to full size. In conse- quence of this I feel reluctant to separate the form as a distinct species, believing that more material will merge the two. I therefore content myself with proposing the name A. argentaria var. ornata." — Gabb, 1876.
Type Locality. — Pataula Creek, Georgia.
Ligament submarginal, lodged in a transverse pit directly beneath the umbone of the left valve ; adductor and byssal scars grouped within an ovate area coated with lime extending from the ligament pit more than half-way to the ventral margin and occupying more than one-half the width of the shell, major byssal scar near the center of the whitish area, slightly ovate in outline; minor byssal scar and adductor ventral to the major cicatrix, subequal in size, semi-elliptical, their straight faces proxi- mate, the adductor the posterior of the two ; major and minor scars united for a short distance along the dorsal face of the latter.
Although most of the individuals which are certainly referable to A. argentaria Conrad develop a faint radial lineation, none in the abund-
MARYLAND GEOLOGICAL SURVEY 613
ant material from the Monmouth of Maryland bridge the gap between that race of argentaria and the costate ornata of Gabb. In fact the dis- tance is greater between Conrad's species and Gabb's than between Gabb's and the A. forteplicata n. sp. A. ornaia has, however, much more of the laminar argentaria texture, a finer and less differentiated radial sculpture and a relatively stronger concentric sculpture than A . forteplicata.
Occurrence. — MONMOUTH FORMATION. Brightseat and McNeys Cor- ners, Prince George's County.
Collections. — Maryland Geological Survey, Philadelphia Academy of Natural Sciences, U. S. National Museum.
Outside Distribution. — Ripley Formation. Exogyra costata zone. Extreme top of zone, Pataula Creek, Georgia.
ANOMIA FORTEPLICATA n. sp.
Plate XXXV, Figs. 7-10
Description. — Shell nacreous, moderately large, rudely circular, sub- circular or irregular in outline; umbones inconspicuous, submarginal, medial in position, apices obtuse ; external surface sculptured with fifteen to forty cordate primary radials and between each pair of primaries one to five secondary lirations of more or less unequal strength; incremental sculpture over-riding the radial but not modifying it to any degree ; liga- ment submarginal, attached beneath the umbone in the left valve ; hinge armature not developed ; adductor and byssal scars grouped within an area thinly coated Avith lime, occupying the medial dorsal half of the shell ; scars brownish in color, three in number, the largest of the three the major byssal scar, minor byssal scar and adductor impression being subequal and ventral to the major cicatrix ; ventral margin sharply crenate in harmony with the external ribbing, the plications reflected on the interior of the shell in some individuals almost to the umbones ; characters of right valve not known. Dimensions.
Altitude 24 mm., latitude 24.5 mm., semi-diameter 6.6 mm.
Altitude 23 mm., latitude 17.5 mm., semi-diameter 7.5 mm.
Altitude 12.7 mm., latitude 14.5 mm., semi-diameter 3.5 mm.
614 SYSTEMATIC PALEONTOLOGY
Although the representatives of this species differ so widely in general aspect, still there seems to be no reason to consider these differences as more than individual mutations of a variable species in a variable genus. The ratio between the number of costals and their prominence is very constant, those individuals in which the primaries are few in number being very heavily sculptured.
Anomia forleplicata is a more solid shell than A. ornata Gabb, with a much more vigorous radial sculpture and a relatively more feeble con- centric.
Occurrence. — MONMOUTH FORMATION. Brightseat, 1 mile west of Friendly, McNeys Corners, Prince George's County.
Collection. — Maryland Geological Survey.
D. Dysodonta
Superfamily MYT1LACEA Family MYTILIDAE
Genus MODIOLUS Lamarck [Prodr. Nouv. Class. Coq., 1799, p. 871
Type. — Mytilus modiolus Linne.
Shell equivalve, inequilateral, transversely or obliquely ovate in outline ; ligament external, opisthodetic ; hinge edentulous ; anterior muscle impres- sion atrophied; pallial line simple.
The genus is separated from Mytilus by the character of the beaks which are non-terminal, wider and rounded anteriorly. It has a long geologic range, at least from the beginning of the Mesozoic and possibly from the Devonian. The recent species are about seventy in number and are most abundant in the tropical seas. Unlike Mytilus, the representatives of Modiolus are nest-builders and burrow or spin a woven structure from stones and fragments of shells.
A. Latitude of adult shell exceeding 20 mm.
1. Shell obtusely angulated at the posterior dorsal extremity.
Modiolus burlingtonensis
2. Shell smoothly rounded at the posterior dorsal extremity.
Modiolus sedesclarus
B. Latitude of adult shell not exceeding 20 mm Modiolus trigona
Etymology: Modiolus, small drinking vase.
MARYLAND GEOLOGICAL SURVEY 615
M.ODIOLUS BURLINGTONENSIS WMtfield
Modiolus burlingtonensis Whitfleld, 1885, Mon. U. S. Geol. Survey, vol. ix,
p. 65, pi. xvii, figs. 8, 9.
Modiolus burlingtonensis Johnson, 1905, Proc. Acad. Nat. Sci., Phila., p. 12. Modiolus burlingtonensis Weller, 1907, Geol. Survey of New Jersey, Pal.,
vol. iv, p. 505, pi. Iv, figs. 18, 19.
Description. — " Shell of moderately large size, very ventricose, and with subparallel dorsal and ventral margins, large prominent umbones and incurved beaks situated near the anterior end but not terminal, the anterior margin perceptibly extending beyond them and rounded. Umbonal ridge prominent and subangular, especially near the beaks, and becoming broader and more rounded posteriorly; surface of the valves strongly constricted and sinuate in front of the ridge and the anterior surface again inflated: cardinal slope comparatively broad and slightly concave toward the postero-cardinal border. Hinge line straight and three-fifths as long as the shell, and rather strongly impressed in the internal cast ; postero-cardinal margin rounding rapidly forward from the more narrowly rounded posterior extremity. Surface of the cast, the only condition under which it is known, apparently smooth or marked only by irregular concentric lines of growth, some of which produce undulations of considerable strength on the casts. On one individual there appear on the posterior cardinal slope very faint indications of rather coarse radiating lines, but too faint to warrant the statement that such markings really existed on the shell."— Whitfield, 1885.
Type Locality. — Burlington County, New Jersey.
The species is much the largest of any of the Matawan Modioli, and is represented in Maryland by only a couple of imperfect casts.
Occurrence. — MATAWAX FORMATION. Camp U & I, opposite Post 192, Chesapeake and Delaware Canal, Delaware.
Collection. — Maryland Geological Survey, Philadelphia Academy of Xatural Sciences.
Outside Distribution. — Matawan Formation. Merchantville clay marl, New Jersey.
616 SYSTEMATIC PALEONTOLOGY
MODIOLUS TRIGONUS n. Sp.
Plate XXXVI, Fig. 3
Description. — Shell thin, nacreous, equivalve, strongly inequilateral, transversely elongate, suggesting a right triangle in outline, the anterior margin constituting the shorter leg, the base line the longer, and the posterior keel the hypothenuse; umbones prominent, acute, prosogyrate, subterminal in position ; anterior margin squarely truncate in front of the umbones; posterior dorsal and lateral margins gently rounded, merging into one another; base line horizontal; posterior keel obtuse, persistent from the umbones to the posterior ventral margin ; area behind it approxi- mately half as great as that in front of it; external surface smooth and lustrous, excepting for feeble incremental striations.
Dimensions. — Altitude 8.5 mm., latitude 14.5 mm., maximum diam- eter 9 mm.
The species is described from a cast of a complete individual, to one side of which the shell substance still adheres. The angular outline is peculiarly characteristic and nothing approaching it has been observed elsewhere.
Occurrence. — MONMOUTH FORMATION. Brooks estate near Seat Pleas- ant, Prince George's County.
Collection. — Maryland Geological Survey.
MODIOLUS SEDESCLARUS n. sp. Plate XXXVI, Figs. 1, 2
Description. — Shell nacreous in texture, exceedingly thin and fragile, transversely elongate, .slightly wider posteriorly; umbones inflated, prosogyrate, almost but not quite terminal in position; anterior end obscurely truncate; dorsal margin slightly more elevated posteriorly; posterior extremity obliquely rounded, the dorsal margin merging smoothly into the lateral; ventral margin straight, not constricted medially; umbonal ridge very prominent but evenly rounded, becoming broader and lower toward the posterior ventral margin ; external surface
MARYLAND GEOLOGICAL SURVEY 617
smooth, excepting for the sharply laminar incremental ridges developed near the dorsal and anterior margins and the prominent growth lines near the ventral margins ; characters of interior not known.
Dimensions. — Altitude 10 mm., latitude 22 mm., maximum diameter 7 mm.
This species is smaller than M. burlingtonensis Whitfield, not con- stricted along the medial ventral margin, and more smoothly rounded behind.
Occurrence. — MONMOUTH FORMATION. Brightseat, Prince George's County.
Collection. — Maryland Geological Survey.
Genus LITHOPHAGA Bolten [Museum Boltenianum, 1788, p. 156]
Type. — Mytilus lithophagus Linne.
Shell thin, nacreous, equivalve, strongly inequilateral, transversely elon- gated, more or less cylindrical in outline ; umbones strongly anterior, but not terminal ; anterior extremity rounded ; posterior extremity rostrate or cuneiform ; external surface smooth or feebly sculptured concentrically ; ligament submarginal; hinge edentulous; muscle impressions unequal, indistinct.
The genus has been reported from strata as far back as the Carbonifer- ous. The recent species number less than fifty, and are confined to the tropical and subtropical waters.
The young are attached by a byssus, but in the later stages usually perforate coral colonies, the shells of larger bivalves or even the solid rock. Two of the five subgenera into which the group has been divided are encrusted with a dense calcareous covering in the adult stages. The cavities which they excavate are characteristically flask-shaped in outline. The perforations in the columns of the temple of Serapis which served Lyell for his classic illustration of changes in the level of the sea were made by Lithophagae.
Etymology: Aitfos, stone; <t>ayeit>, to eat.
618 SYSTEMATIC PALEONTOLOGY
A. Shell encrusted with concentrically laminated calcareous covering.
Lithophaga ripleyana
B. Shell not encrusted.
1. Latitude of adult shell not exceeding 18 mm.
a. Outline subcylindrical.
i. Shell occurring in hard substances especially in the tests
of larger bivalves Lithophaga concha fodentis
ii. Shell occurring free or in clay tubes Lithophaga julice
b. Outline transversely ovate Lithophaga lingua
2. Latitude of adult shell exceeding 18 mm.; outline subcylindrical.
Lithophaga twitchclH
LITHOPHAGA EIPLEYAXA Gabb Plate XXXVI, Figs. 4-6
Lithophaga ripleyanus Gabb, 1862, Proc. Acad. Nat. Sci., Phila. for 1861, p.
326. Lithophaga ripleyanus Meek, 1864, Check List Inv. Fossils, N. A., Cret. and
Jur., p. 10.
Lithophaga ripleyana Gabb, 1876, Proc. Acad. Nat. Sci., Phila., p. 311. Lithodomus ripleyana Whitfield, 1885, Mon. U. S. Geol. Survey, vol. ix, p. 67,
pi. xvii, figs. 4, 5 (ex parte).
Lithophaga ripleyana Johnson, 1905, Proc. Acad. Nat. Sci., Phila., p. 13. Lithophaga ripleyana Weller, 1907, Geol. Survey of New Jersey, Pal., vol.
iv, p. 512, pi. Ivi, figs. 9-12 (ex parte).
Description. — " Tube subcylindrical, nearly straight, gradually taper- ing, broadest on the dorsal surface ; opposite face narrow, rounded ; extremity abrupt, rounded and faintly subtrilobate. Shell subquadrate. Beaks terminal, and projecting beyond the buccal end of the shell, very much incurved, so as to appear somewhat spiral. Umbones broad, slightly flattened in the middle. Cardinal margin straight anteriorly, depressed posteriorly, merging into the anal border, which is subtruncate and most prominent above. Basal edge broadly emarginate. Surface marked by numerous, irregular, concentric lines." — Gabb, 1860.
Type Locality. — Big Timber Creek, between Gloucester and Red Bank, New Jersey.
Form gregarious, rudely cylindrical, constricted mesially; protective covering built up of thin, concentric layers of calcite, usually conforming rather closely to the outline of the shell ; shell itself very thin, nacreous in texture; umbones terminal, prosogyrate, well rounded at their tips; anterior portion inflated, truncate; shell, in the majority of the indi-
MARYLAND GEOLOGICAL SURVEY 619
viduals, feebly depressed in front of the obscure carina which extends from the umbones toward the posterior ventral margin, the depression being reflected in the slight concavity of the base ; posterior end strongly and symmetrically arcuate; dorsal margin approximately horizontal; external surface smooth excepting for the incremental sculpture which is rather conspicuous, particularly in the posterior portion of the shell; characters of interior not known.
The species frequently occurs in clusters, the individuals being attached at the posterior extremity. The degree of medial constriction is not constant.
L. ripleyana Gabb is relatively more elongated transversely than L. affinis Gabb, a co-existent species over much of the area of its occurrence, and is much less inflated.
Occurrence. — MATAWAN FORMATION. Opposite Post 239, Post 236, Camp Fox, Chesapeake and Delaware Canal, Delaware. MONMOUTH FOR- MATION. Bohemia Mills, Cecil County; Brightseat, Brooks estate near Seat Pleasant, Friendly, Prince George's County, Maryland.
Collections. — Maryland Geological Survey, Philadelphia Academy of Natural Sciences, New Jersey Geological Survey, U. S. National Museum.
Outside Distribution. — Matawan Formation. Merchantville clay marl, Wenonah sand, New Jersey. Monmoutli Formation. Navesink marl, New Jersey. Ripley Formation. Exogyra costata zone, Union County, Mis- sissippi.
LlTHOPHAGA CONCHAFODENTIS n. Sp.
Plate XXXVI, Figs. 7-9
Description. — Shell nacreous in texture, moderately large for the genus, subcylindrical to rectangular in outline, exceedingly thin and fragile; umbones nearly terminal, small, full but angular, flattened upon their summits, acute, prosogyrate ; posterior area cut off by a carina which per- sists from the umbones to the posterior basal margin, acute near the umbones, but evanescing toward the base; anterior end very short and obscurely truncate ; posterior end much produced, strongly rounded at its extremity; the dorsal and ventral margins rudely parallel, the dorsal
41
620 SYSTEMATIC PALEONTOLOGY
slightly convex, the ventral broadly and feebly constricted ; external sur- face smooth excepting for a rather vigorous incremental sculpture; liga- ment submarginal, opisthodetic ; hinge edentulous; adductor scars and pallial characters obscure.
Dimensions. — Altitude 5 ± mm., latitude 13 ± mm., semi-diameter 3.5 ± mm.
The remains of this small borer are found in the tests of Exogyra and Pycnodonte. It differs from L. ripleyana, which it most strongly resembles, not only in its habitat but also in the less inflated valves and less produced posterior extremity.
Occurrence. — MONMOUTH FORMATION. Brightseat, Prince George's County.
Collection. — Maryland Geological Survey.
LITHOPIIAGA JULIJE (Lea) Plate XXXVI, Figs. 10, 11
Modiola Julia; Lea, 1862, Proc. Acad. Nat. Sci., Phila. for 1861, p. 149. Modiolus Julice Meek, 1864, Check List. Inv. Fossils N. A., Cret. and Jur.,
p. 11.
Perna Julite Conrad, 1868, Cook's Geol. of New Jersey, p. 726. Modiola Julia Whitfield, 1885, Mon. U. S. Geol. Survey, vol. ix, p. 64, pi. xvii,
fig. 6 (not fig. 7).
Modiolus Julia Johnson, 1905, Proc. Acad. Nat. Sci., Phila., p. 12. Modiolus Julicc Weller, 1907, Geol. Survey of New Jersey, Pal., vol. iv, p. 506
(ex parte, description and figures excluded).
Description. — " Testa transverse striata, subrhomboidea, subinflata, postice oblique truncata, inferne emarginata; valvulis fragillissimis; nati- bus prominulis, fere terminalibus. Length .23, breadth .36 of an inch." —Lea, 1862.
Type Locality. — Haddonfield, New Jersey.
Shell nacreous, excedingly thin and friable ; transversely ovate in out- line, compressed ; umbones placed within the anterior seventh of the shell, not prominent but evenly rounded, proximate, incurved and slightly prosogyrate ; anterior end of shell feebly expanding in front of the beaks ; posterior dorsal margin approximately horizontal; posterior lateral mar-
MARYLAND GEOLOGICAL SURVEY 621
gin quite strongly rounded, obliquely produced at the base ; ventral mar- gin somewhat oblique to the dorsal; posteriorly produced, in many indi- viduals feebly and broadly contracted medially ; basal constriction due to the broad and very shallow depression of the valves in front of the obtuse posterior carina which is initiated at the umbones and most prominent at its origin, becoming feebler and finally evanescing about half-way to the posterior ventral margin; external surface sculptured with sharp, rather distant and irregularly spaced incremental lirations which tend to become obsolete upon the medial portion of the shell; characters of interior of shell not known.
Casts of this small form are not rare in the Upper Cretaceous of Mary- land, although the shell is so thin and so flaky that it has not been found possible to secure any fragments large enough to give the hinge dentition, yet the exceedingly thin and very highly nacreous shell and its general outline suggest Lithophaga rather than Modiolus. The form is much more compressed than L. ripleyana Gabb, the umbones more flattened and the posterior carina more angular. Furthermore there is no evidence that a calcareous encrustation was ever developed as in the Kipley species, but rather that it buried itself in the soft muds near the shore.
Whitfield's restoration of Gabb's type is probably inaccurate as the material is much crushed and the original outline obscure.
Occurrence. — MOXMOUTH FORMATION. Brightseat, Brooks estate near Seat Pleasant, Prince George's County.
Collections. — Maryland Geological Survey, Philadelphia Academy of Xatural Sciences, New Jersey Geological Survey.
Outside Distribution. — Matawan Formation. Merchantville clay marl, and Woodbury clay, New Jersey.
LITHOPHAGA LINGUA n. sp. Plate XXXVI, Fig. 14
Description. — Shell small, compressed, not very thin, transversely and somewhat obliquely ovate in outline; umbones anterior, almost but not quite terminal, well rounded, but not conspicuously inflated, proximate,
622 SYSTEMATIC PALEONTOLOGY
incurved, prosogyrate ; valves flattening in all directions away from the umbones ; anterior end very short, rounded ; posterior end obliquely pro- duced along the obscurely elevated diagonal from the umbones to the pos- terior ventral margin ; posterior dorsal and lateral areas relatively very wide, their margins forming a somewhat asymmetrical arc connecting the umbones and the base ; ventral margin slightly oblique with a feeble sug- gestion of a mesial constriction; faint concentric sculpture probably developed on external surface; characters of hinge and interior not known.
Dimensions. — Maximum altitude 5 mm., maximum latitude 8 mm., maximum diameter 3.5 mm.
This small but apparently adult Lithophaga is separated from the co- existent members of the same genus not only by its slight dimensions but even more readily by the very short anterior end and expanded posterior end. In no other species is the area behind the diagonal relatively so wide or so flaring. The peculiar alate aspect thus produced is not repeated in any of the co-existent species. The form is described from a cast of double valves. The type is not unique, but the species has not been observed from any but the type locality.
Occurrence. — MONMOUTH FORMATION. Brightseat, Prince George's County.
Collection. — Maryland Geological Survey.
LITHOPHAGA TWITCHELLI n. sp. Plate XXXVI, Figs. 12, 13
Description. — Shell nacreous, apparently rather thick, large for the genus, subcylindrical in outline ; umbones inflated, incurved, prosogyrate, proximate, placed within the anterior tenth; shell inflated along the diagonal from the umbones to posterior ventral margin, broadly and shallowly depressed between this obscure carina and the feebly inflated anterior end; anterior lateral margin obscurely truncate, posterior strongly arcuate; dorsal margin very feebly convex; base line somewhat constricted medially ; external surface probably smooth ; characters of interior of shell not known.
MARYLAND GEOLOGICAL SURVEY 623
Dimensions. — Altitude 11.8 mm., latitude 21.8 mm., diameter of double valves 11.7 mm.
Lithophaga twitchelli suggests, at first, a giant L. ripleyana Gabb. How- ever, L. twitchelli is not only a third as large again as Gabb's species, but, furthermore, the valves are very much more inflated, particularly along the diagonal; the umbones feebler and the medial depression more pro- nounced. Then, too, the shell is much heavier, apparently, and there is no evidence of the former presence of an encrustation.
This species is named for its collector. Dr. Mayville W. Twitchell, Assistant State Geologist of New Jersey.
The form is described from a cast of the double valves of a single indi- vidual to which a considerable amount of shell substance still adheres, although the external surface has been entirely decorticated.
Occurrence. — MONMOUTH FORMATION. Eailroad cut west of Seat Pleasant, Prince George's County.
Collection. — Maryland Geological Survey.
Genus CRENELLA Brown
[111. Conch. Gr. Brit., 1827, pi. xxxi, figs. 12-14; 2d ed., 1844, p. 75, pi. xxiii, figs. 12-14. Not Crenella Sowerby]
Type. — Mytilus decussatus Laskey.
" Shell oblong-oval, equilateral, ventricose ; beaks obtuse, slightly turned to one side; hinge destitute of teeth but with a flattened, horizontal, slightly crenated plate on one side of the hinge in each valve ; right valve with a triangular, horizontal, projecting, reflexed plate, and the left one witli an oblique plate, both of which are a little crenated externally ."- Brown, 1844.
" This interesting little group extends through the Tertiary and, owing to the little study given to its characters, has received many names. The shell is usually convex and ovoid, with more or less incurved beaks, a nacreous inner layer, thin epidermis which adheres closely to the shell, and a fine radial, often crossed by a concentric striation. In young shells the provinculum is exceptionally well developed, sometimes recalling the
Etymology: Diminutive of crena, notch.
624 SYSTEMATIC PALEONTOLOGY
hinge of Nucula by its strong and projecting denticulations. If the shell is thin, these become obsolete with growth, but in some species are replaced by a series of denticulations directly consequent on the impingement of the external sculpture on the cardinal margin, thus repeating a second time in the same individual the process by which the provinculum was originally initiated in its ancestors. At least that is the way in which the writer interprets the facts. When the shell is thick, or when the external sculpture is very delicate, no secondary denticulations appear in the adult, which is then left with a practically unarmed hinge line. The appearance of the provinculum is not dependent on the existence of the external sculpture, but the secondary denticulations are so dependent. The exte- rior may be almost perfectly smooth and polished with only microscopic striation; finely radially striate without decussation (like C. serica), decussate, or with the radial sculpture strong and divaricate. Usually the sculpture is uniformly distributed over the surface, but occasionally there will be an area of unstriated separating two of striated surface, as in Modiolaria, but without the impressed boundaries of the latter genus."- Dall, 1898.1 This genus ranges from the Cretaceous to the Recent.
A. Adult shell not exceeding 6 mm. in altitude Crenella serica
B. Adult shell exceeding 6 mm. in altitude Crenella elegantula
CRENELLA SERICA Conrad Plate XXXVI, Figs. 16-18
Crenella (Stalagmium) serica Con., 1860, Jour. Acad. Nat. Sci., Phila., 2d
ser., vol. iv, p. 281, pi. xlvi, fig. 23. Crenella (Stalagmium) sericea Meek, 1864, Check List Inv. Fossils, N. A.,
Cret. and Jur., p. 11. Crenella serica Weller, 1907, Geol. Survey New Jersey, Pal., vol. iv, p. 510,
pi. Ivi, figs. 7, 8.
Description. — " Longitudinally oblong-ovate, very ventricose, finely striated concentrically and with microscopic, closely arranged, radiating lines; summit very prominent. Locality: Eufaula, Barbour County, Alabama." — Conrad, 1860.
1 Ball, W. H., Trans. Wagner Free Inst. Sci., Phila., vol. iii, pt. iv, p. 802.
MARYLAND GEOLOGICAL SURVEY 625
Shell very small and gibbous, between three and four millimeters in altitude, the interior regularly ovate in outline; umbones inflated, strongly prosogyrate and incurved, proximate ; external surface sculptured with prominent and regularly spaced incrementals and resting stages; radial sculpture microscopically fine, not over-riding the concentric ; liga- ment lodged in a narrow groove running backward from beneath the apices of the umbones ; inner margins strongly crenulate, the area directly beneath the umbones slightly flattened and broadened and bearing four or five pseudo-taxodont denticles; a more extended, but less clearly defined, area developed in some individuals upon the medial portion of the pos- terior lateral margin ; muscle scars and pallial lines indistinct. Crenella serica Con. is a very abundant little bivalve in the Monmouth of Prince George's County.
Occurrence. — MONMOUTH FORMATION. Brightseat, Brooks estate near Seat Pleasant, Friendly, 1 mile west of Friendly, Prince George's County.
Collections. — Maryland Geological Survey, New Jersey Geological Sur- vey, U. S. National Museum.
Outside Distribution. — Matawan Formation. Marshalltown clay marl. New Jersey. Monmouth Formation. Eed Bank sand, New Jersey. Peedee Sand. North and South Carolina. Ripley Formation. Exogyra costata zone, Georgia ; Eufaula, Alabama. Selma Chalk. Exogyra costata zone, Tombigbee Eiver, Sumter County, Alabama; east-central Missis- sippi ; Alcorn, Union and Tippah counties, Mississippi. Extreme top of zone, Pataula Creek, Georgia; Lowndes County, Mississippi.
CRENELLA ELEGANTULA Meek and Hayden Plate XXXVI, Fig. 19
Crenella elegantula Meek and Hayden, 1862, Proc. Acad. Nat. Sci., Phila.,
for 1861, p. 441. Crenella elegantula Meek, 1864, Check List Inv. Fossils, N. A., Cret. and
Jur., p. 11. Crenella elegantula Meek, 1876, Kept. U. S. Geol. Survey, Territories, vol.
ix, p. 75, pi. xxviii, figs. 6a-6c. Crenella elegantula Weller, 1907, Geol. Survey New Jersey, Pal., vol. iv, p.
511, pi. Ivi, fig. 6.
626 SYSTEMATIC PALEONTOLOGY
Description. — " Shell small, very thin and pearly, obliquely ovato- cordate, ventricose ; postero-basal and basal margins rounded ; dorsal border sloping posteriorly with an arcuate outline, and rounding into the anal margin behind; anterior border rounding obliquely backwards into the base; umbonal region of both valves very gibbous, beaks prominent, terminal, pointed, distinctly incurved and directed obliquely forward at the extremities; hinge margin smooth ; free border minutely crenulated. Sur- face (as seen by aid of a magnifier) beautifully ornamented by extremely fine, regular, closely-arranged, radiating striae, which increase chiefly by bifurcation, and continue of 'uniform size on all parts of the shell ; cross- ing these are numerous, equally fine, but much less distinct, concentric lines, and occasional stronger marks of growth. Length, measuring obliquely forward and upward from the base to the beaks, 0.55 in. ; diam- eter, from base to hinge, measuring at right angles to the greatest length, 0.4 inch; convexity, 0.37 inch. This beautiful little shell is very closely allied to C. sericea of Conrad, but differs in being uniformly more broadly ovate in form, and in having less elevated and less distinctly incurved beaks, while its concentric markings are not near so strongly defined."- Meek and Hayden, 1862.
Type Locality. — Deer Creek, near North Branch of the Platte Eiver, Nebraska.
The species is recognized in Maryland from casts only. It is more than double the size of C. serica Conrad, relatively broader, and less inflated and less prominently sculptured concentrically.
Occurrence. — MONMOUTII FORMATION. Brightseat, Prince George's County.
Collections. — Maryland Geological Survey, New Jersey Geological Sur- vey, U. S. National Museum.
Outside Distribution. — Monmouth Formation. Tinton beds. New Jersey. Ripley Formation. Exogyra costata zone, ? Owl Creek, Tippah County, Mississippi. Fox Hills Sandstone. Western Interior.
MAEYLAND GEOLOGICAL SURVEY 627
Family DREISSENIIDAE
Genus DREISSENA Van Beneden [Ann. Sci. Nat, ser. 2, vol. iii, 1835, p. 193, pi. viii]
Type. — Mylilus polymorplius Pallas.
Equivalve, inequilateral, slightly gaping as a rule, mytiliform in out- line ; umbones acute, terminal, bent a little forward ; anterior area differ- entiated by a more or less obtusely angulated keel which runs from the umbones to the anterior ventral margin ; external surface smooth or incre- mentally sculptured ; ligament internal or submarginal, lodged in a shal- low groove, which extends more than a third of the way down to the base: angle between the umbones bridged by a transverse septum upon which the anterior and pedal adductors are mounted and from which, in the right valve, a small dentiform process sometimes projects ; posterior adductor scar moderately large, well down towards the base; pallial line rather obscure, entire.
Dreissena is very like Mytilus in general aspect, so much so, indeed, that there is probably a considerable amount of confusion between the two genera in the earlier described species. Many authorities maintain that the genus is not initiated until the Early Tertiary. Henry Woods,1 how- ever, has reported a species, I>reissensia lanceolata (Sowerby) Woods from the Cretaceous of England, and has so adequately figured it that there can be no doubt about the correctness of his determination.
The shell differs most conspicuously from that of Mytilus in the devel- opment of the septum in the umbonal angle and the more internal liga- ment. The animal differs from that of Mytilus in the closed mantle and the two distinct siphons. All of the recent species are denizens of fresh or brackish water.
Etymology: Named in honor of Dreissens, a Belgian physician. 1 1900, Mon. Cret. Lamellibranchia, England, Paleontographical Soc., Lon- don, pt. ii, p. 110, pi. xviii, figs. 13-15; pi. xix, figs. 1-11.
628 SYSTEMATIC PALEONTOLOGY
DREISSENA TIPPANA Conrad Plate XXXVII, Figs. 8-11
Dreissena tippana Conrad, 1858, Jour. Acad. Nat. Sci., Phila., vol. Hi, p.
328, pi. xxxiv, fig. 14. Dreissena tippana Meek, 1864, Check List Inv. Fossils, N. A., Cret. and Jur.,
p. 10.
Description. — " Falcate, with distinct lines of growth; front excavated, the margin acutely angular ; the dorsal and posterior margin form a regu- lar curve; base rounded; beaks acute." — Conrad, 1858.
Type Locality. — Owl Creek, Tippah County, Mississippi.
Shell thick, prismatic, strongly falcate in outline, evenly convex, acutely keeled from the umbones to the ventral margin, the carinal angle usually more than 90° and giving to the front view of the double valves a canoe-shaped outline; outline of posterior margin evenly rounded from beaks to base; external surface smooth except for incremental striations and, toward the ventral margin, rather pronounced resting stages; liga- ment groove rather shallow and elongated, hinge edentulous; umbonal septum narrow but quite high ; character of muscle impressions and pallial sinus not preserved ; inner margins simple.
In Maryland the species is represented chiefly in the form of casts, most frequently of the double valves, to which portions of the brown, prismatic shell substance still adhere, although at some localities perfect specimens have been collected. The form differs quite widely in relative proportions, but it does not seem wise to regard these mutations as of more than indi- vidual import.
Occurrence. — MATAWAN FORMATION. Ulmstead Point, Anne Arundel County. MONMOUTH FORMATION. ? Fredericktown, Cecil County; Brightseat, Brooks estate near Seat Pleasant, 1 mile west of Friendly, Prince George's County.
Collections. — Maryland Geological Survey, U. S. Xational Museum.
Outside Distribution. — Ripley Formation. Exogyra costata zone, Georgia; Eufaula, Alabama; Union and Tippah Counties, Mississippi. Extreme top of zone, Pataula Creek, Georgia ; Chattahoochee River, Ala- bama.
MARYLAND GEOLOGICAL SURVEY 629
order ANOMALODESMACEA Superfamily ANATINACEA
Family PHOLADOMYIDAE
Genus PHOLADOMYA Sowerby [Genera Recent and Fossil Shells, 1825, pp. 235, 236, pi. xxxvii]
Type. — Plioladomya Candida Sowerby.
" The following generic character being drawn up principally from the recent specimen, several particulars will be mentioned in it which cannot be observed in the fossils ; there is not, however, the smallest doubt as to their generic identity. Shell very thin, rather hyaline, transverse, ventri- cose ; inside pearly ; posterior side short, sometimes very short, rounded ; anterior side more or less elongated, gaping; upper edge also gaping a little ; hinge with a small rather elongated, triangular pit, and a marginal lamina in each valve, to the outer part of which is attached the rather short external ligament. Muscular impressions two ; these, as well as the muscular impression of the mantle, in which there is a large sinus, are indistinct. This shell is the only instance we have ever seen in which the umbones are so approximated as to be worn through by the natural action of the animal in opening and closing its valves." — Sowerby, 1825.
Equivalved or subequivalved, inequilateral, transversely elongated or subtrigonal, gaping posteriorly and sometimes anteriorly as well ; umbones inflated, anterior ; external sculpture radial, often more or less nodose ; ligament short, external, opisthodetic ; cardinal margin often reflected to form a false area behind the umbones ; hinge edentulous excepting a single subumbonal tubercle and pit in each valve; muscle impressions obscure, two in number ; pallial sinus profound.
The genus was initiated early in the lower Lias, and though it culmi- nated later in the Jurassic, the decline was not marked until the close of the Mesozoic. The Tertiary representation, however, was very meager and less than half a dozen species have persisted to the present day. As in so many of the ancient types, the few survivors have retreated to unf avor-
Etymology: A name suggested by " its resemblance to shells of two Lin- nean genera, the Pholades and Mya."
630 SYSTEMATIC PALEONTOLOGY
able regions where the struggle for existence is less keen and they do not have to compete with more virile groups. The few recent forms, including the generic type, P. Candida Sowerby, inhabit the ocean depths, some of them below the one thousand fathoms line. A single species has been recorded off the Japan coast, one from off the Africa coast and the rest from the Antillean region.
A. Outline subcylindrical ; umbones broad, rounded, not conspicuously
high Pholadomya occidentalis
B. Outline ovate-trigonal; umbones relatively narrow, subangulated, con-
spicuously high Pholadomya conradi
PHOLADOMYA OCCIDENTALIS Morton Plate XXXVII, Figs. 1-3
Pholadomya occidentalis Morton, 1833, Am. Jour. Sci., 1st ser., vol. xxiii,
p. 292, pi. viii, fig. 3. Pholadomya occidentalis Morton, 1834, Syn. Org. Rem. Cret. Group, U. S.,
p. 68, pi. viii, fig. 3. Pholadomya occidentalis Meek, 1864, Check List Inv. Fossils, N. A., Cret.
and Jur., p. 14 (ex parte).
Pholadomya occidentalis Conrad, 1868, Cook's Geol. of New Jersey, p. 727. Pholadomya occidentalis Whitfield, 1885, Mon. U. S. Geol. Survey, vol. ix,
p. 175, pi. xxiv, figs. 1-3.
Pholadomya occidentalis Johnson, 1905, Proc. Acad. Nat. Sci., Phila., p. 13. Pholadomya occidentalis Weller, 1907, Geol. Survey of New Jersey, Pal.,
vol. iv, p. 513, pi. Ivi, figs. 1-3. (Synonymy excluded.)
Description. — " Oblong-angular, ventricose near the beaks ; with twenty-five to thirty narrow, elevated, subtortuous costae, having broad, slightly concave intervening spaces. Length 2 inches, breadth 3 inches. An extremely variable species. I possess five specimens (all more or less broken), in all of which there is a difference in the number and relative position of the ribs." — Morton, 1833.
Type Locality. — Chesapeake and Delaware Canal.
" The dimensions of an average-sized specimen are : Length about 70 mm., height 47 mm., thickness 45 mm. Shell subovate or sub- elliptical in lateral outline, and cordate from in front. Hinge line straight, about two-thirds as long as the shell ; anterior margin rounding from the cardinal extremity into the basal margin, or obliquely subtrun-
MARYLAND GEOLOGICAL SURVEY 631
cate; basal margin gently convex, becoming straighter posteriorly; pos- terior margin more narrowly rounded than the anterior. Beaks large and broad, situated from one-fifth to one-fourth the length of the shell from the anterior extremity, strongly incurved and nearly in contact, moder- ately elevated above the hinge line. Valves most prominent at about their mid-height in front of the middle of the shell; from this point the surface curves rather abruptly to the ventral anterior and cardinal mar- gins, and much more gently to the gaping posterior margin ; the cardinal margins back of the beaks are slightly inflected to form a rather distinct, concave cardinal area of moderate width on each valve. Surface of each valve marked by twenty-five or thirty more or less irregular and wavy, rounded, radiating costse of moderate strength, much narrower than the intervening depressions, and closer together in the middle of the shell than at either the anterior or posterior portions ; in the middle of the shell every other costa on large individuals has usually been intercalated between two others at some distance below the beak; the shell is also marked by more or less irregular, concentric undulations. This species is one of the most characteristic members of the Merchantville clay marl fauna, where it sometimes occurs in considerable numbers." — Weller, 1907.
The species is not known from Maryland, but it occurs in the form of poorly-preserved casts along the Chesapeake and Delaware Canal in Dela- ware. It is readily recognizable by the well-rounded gibbous valves and the irregular elevated radial lirse. The more southern and apparently later P. Conradi described by Conrad under the name of P. occidentalis has been accepted as a synonym by the later workers, although the two shells are obviously distinct. The northern form runs larger than the southern, is much more nearly cylindrical and less trigonal in outline, the umbones are broader, more evenly rounded, set farther back from the ante- rior extremity and very much less prominent.
Occurrence. — MATAWAX FORMATION. Posts 218 and 105, Briar Point, Post 156, Chesapeake and Delaware Canal, Delaware.
Collections. — Maryland Geological Survey, Philadelphia Academy of Natural Sciences, New Jersey Geological Survey.
632 SYSTEMATIC PALEONTOLOGY
Outside Distribution.-— Magothy Formation. Cliffwood clay, New Jersey. Matawan Formation. Merchantville clay marl, Woodbury clay, New Jersey.
PHOLADOMYA CONRADI n. sp. Plate XXXVIII, Fig. 1
Pholadomya occidentalis Conrad, 1860, Jour. Acad. Nat. Sci., Phila., 2d ser.,
vol. iv., p. 276. Pholadomya occidentalis Owen, 1860, 2d Kept. Geol. Recon. Ark., pi. viii,
fig. 9.
Description. — " Subovate, very inequilateral, inflated anteriorly ; ribs about twenty-five, irregular, prominent, acute, posteriorly distant, crenu- latecl by rugose concentric striae, on the umbo tuberculato-crenate ; summit very prominent; anterior margin obliquely truncated. Length 3£ inches, height 2| inches.'' — Conrad, 1860.
Type Locality. — Tippah County, Mississippi.
Shell very thin and nacreous, approximately equivalve, very inequi- lateral ; umbones rather narrow and compressed, obtusely angulated, rising high above the dorsal margin, almost at the anterior extremity ; anterior end broadly and very feebly arcuate; posterior end symmetrically pro- duced and strongly arcuate; external surface sculptured with twenty-five or twenty-six sharply elevated radial lirae, beaded in the umbonal region by the intersecting incrementals and minutely undulated by the growth sculpture even to the ventral margin.
Pholadomya conradi n. sp. has been confused with P. occidentalis Morton, so characteristic of the Xew Jersey and Delaware Matawan. The later species (P. conradi) runs smaller and is less inflated in general out- line, while the very high, rather narrow, subangulated umbones, rising from the extreme anterior end of the shell, lend it an aspect that is very characteristic and quite distinct from the subcylindrical outline of P. occi- dantalis Morton.
Occurrence. — MONMOUTH FORMATION. Brightseat, Prince George's County.
Collections. — Maryland Geological Survey, U. S. National Museum.
MARYLAND .GEOLOGICAL SURVEY 633
Outside Distribution. — Ripley Formation. Exogyra costata zone, Eufaula, Alabama ; Union and Tippah counties, Mississippi. Extreme top of zone, Chattahoochee River, Alabama.
Family ANATINIDAE
Genus PER1PLOMYA Conrad [Am. Jour. Conch., July, 1870, vol. vi, p. 76]
= Leptomya Conrad, 1867. Not Leptomya A. Adams, 1864.
= Plicomya Stoliczka, November, 1870.
Type.— Periploma appUcata Conrad.
" Elongated, inequivalve, thin, perlaceous, gaping anteriorly ; hinge with a projecting spoon-shaped cartilage process, narrowing gradually towards the inferior end, which is acutely rounded; this process joins an oblique callosity which extends to the cardinal margin ; an obsolete rib and fissure run obliquely from the anterior side of the apex. This genus, which is allied to Anatina, differs from it in having a tapering cartilage process attached to a rib or support which joins the hinge margin ante- riorly; and in having the fissure anterior to the apex, and running obliquely towards the anterior extremity of the ventral margin. This genus is known in this country only by one species, which is found in the Eipley group of the Cretaceous era. Judging from external characters and outline of the shells, I should suppose that d'Orbigny's Periploma robi- naldina, P. necomiensis and P. simplex are species of Leptimya, which genus probably became extinct with the Cretaceous fauna. The gape of the anterior is moderate, and valves but slightly reflexed, in which respects it differs essentially from Anatina"1 — Conrad, 1867.
FEUIPLOMYA ELLIPTICA Gabb
Anatina elliptica Gabb, 1862, Proc. Acad. Nat. Sci., Phila. for 1861, p. 324. Anatina elliptica Meek, 1864, Check List Inv. Fossils, N. A., Cret. and Jur., p. 15.
Etymology: (?)A name suggested by the resemblance of the form to Periploma and Mya.
1 Conrad, 1867, Am. Jour. Conch., vol. iii, p. 15.
634 SYSTEMATIC PALEONTOLOGY
Anatina elliptica Conrad, 1868, Cook's Geol. of New Jersey, p. 727. Periplomya elliptica Gabb, 1876, Proc. Acad. Nat. Sci., Phila., p. 305. Periplomya elliptica Whitfield, 1885, Mon. U. S. Geol. Survey, vol. ix, p. 177,
pi. xxiii, figs. 14, 15.
Periplomya elliptica Johnson, 1905, Proc. Acad. Nat. Sci., Phila., p. 13. Periplomya elliptica Weller, 1907, Geol. Survey of New Jersey, Pal., vol. iv, p. 522, pi. Ivii, figs. 8-11.
Description. — " Shell subelliptical, equivalve, nearly equilateral ; beak central, pointing posteriorly, very small, umbones small. Cardinal mar- gin slightly convex. Buccal margin broad, nearly straight and sloping inwards towards the basal edge, which is very broadly rounded, being nearly straight just opposite the beaks. Anal extremity hardly more than half as broad as the buccal, and with the hinge line between it and the beaks, regularly concave. There is a broadly rounded ridge extending from the umbones towards the anterior basal margin, gradually becoming obsolete as it approaches the edge. Shell thin, and marked on the surface by small, irregular concentric ridges. Length 0.9 inch (from beaks to basal margin), width 1.3 inch."— Gabb, 1862.
Type Locality. — Mullica Hill, New Jersey.
" Shell small, inequivalve, and very inequilateral, subovate in outline, largest across the anterior side of the beaks, and strongly constricted just behind them, the posterior end being narrowed on the hinge line and exca- vated at this point. Valves somewhat ventricose, the right one less con- vex than the left, and very decidedly depressed in the central region and toward the basal line, showing a decided twist or arcuation of the valves as seen in a basal view. Anterior end broadly rounded, and the posterior pointedly rounded. Beaks small, appressed, incurved, and apparently directed backward, as is usual in this group of shells, from the expansion of inflation of the anterior side of the hinge line. Cardinal margin, as seen on the cast, inflected both in front of and behind the beaks, forming an apparent lunule and escutcheon on the cast, probably produced mainly from a thickening of the hinge plate within. Muscular imprints and pallial line and hinge not observed." — Whitfield, 1885.
A single imperfect cast has been referred to this species. It shows, however, the compressed valves, the acute umbones and the constriction behind the umbones which characterize the species.
MARYLAND GEOLOGICAL SURVEY 635
Occurrence. — MONMOUTH FORMATION. Brooks estate near Seat Pleas- ant, Prince George's County.
Collections. — Maryland Geological Survey, Philadelphia Academy of Natural Sciences.
Outside Distribution. — Manasquan Formation. ? New Jersey.
Superfamily ENSIPHONACEA Family POROMYACIDAE
Genus LIOPISTHA Meek [Check List Invt. Foss. N. A., Cret. and Jur., 1864, p. 32]
Type. — Cardium elegantulum Eoemer.
" Shell equivalve, inequilateral, transversely subovate, being usually narrower, more compressed, and often subrostrate behind, and ventricose in the central and umbonal regions, nearly always extremely thin; extremities rounded in outline, the posterior side usually a little gaping ; surface granular, and varying, according to the sections and species, from radiately costate on the flanks and front of the valves, to strongly undu- late concentrically, with only a few impressed, radiating lines on the middle, or rarely nearly smooth, concentrically striate, or furrowed, with obsolescent radiating striae ; dorsal margins generally inflected so as to form a sort of false area along its entire length ; hinge with two promi- nent cardinal teeth projecting out at right angles from close up under the hinge line, beneath the beak of the right valve (the posterior tooth being larger and compressed, and the anterior pointed), and one promi- nent and one rudimentary cardinal tooth under that of the left; lateral teeth, none; ligament external; fulcra short and erect. Pallial line unknown.
" Liopistha Meek (typical). — Shell transversely subovate, ornamented, excepting on the posterior dorsal portions of the valves, by regular, simple, well-defined, sometimes subcrenate, radiating costa?." — Meek, 1876.1
The genus is restricted in its distribution to the Cretaceous.
A. Secondary radial sculpture not developed Liopistha protexta
B. Secondary radial sculpture developed Liopistha alternata
Etymology: Xeios, smooth; S-n-iffOei', behind. 1 U. S. Geol. Survey Terr., vol. ix, p. 227.
42
G36 SYSTEMATIC PALEONTOLOGY
LIOPISTHA PKOTEXTA Conrad Plate XXXVI, Fig. 15
Cardium, protextum Conrad, 1853, Jour. Acad. Nat. Sci., Phila., 2d ser., vol.
ii, p. 275, pi. xxiv, fig. 12. Fragilia protexta Conrad, 1860, Jour. Acad. Nat. Sci., Phila., 2d ser., vol.
iv, p. 275. Papyridea (Liopistha) protexta Meek, 1864, Check List Inv. Fossils, N. A.,
Cret. and Jur., p. 12.
Liopistha protexta Conrad, 1868, Cook's Geol. of New Jersey, p. 726. Liopistha protexta Meek, 1876, Kept. U. S. Geol. Survey, Territories, vol.
ix, p. 227; text figs. 20-24. Liopistha protexta Whitfield, 1885, Mon. U. S. Geol. Survey, vol. ix, p. 140,
pi. xx, figs. 1-3. Liopistha inflata Whitfield, 1885, Mon. U. S. Geol. Survey, vol. ix, p. 142,
pi. xx, figs. 4, 5.
Liopistha protexta Johnson, 1905, Proc. Acad. Nat. Sci., Phila., p. 13. Liopistha protexta Weller, 1907, Geol. Survey of New Jersey, Pal., vol. iv,
p. 526, pi. Iviii, figs. 4-6.
Description. — " Suboval or subtriangular, inequilateral, ventricose ; ribs about twenty-eight in number, narrow, rounded, obsolete on the posterior subraargin; posterior extremity obliquely truncated; beaks prominent ; basal margin rounded ; umbonal slope undefined ; posterior end gaping. (A cast.) " — Conrad, 1853.
Type Locality. — Burlington County, New Jersey.
Shell of moderate size and rather heavy for the genus, gaping pos- teriorly, transversely ovate-trigonal in outline, evenly inflated, the maxi- mum diameter falling near the medial portion of the shell; umbones evenly rounded, the apices proximate, incurved and feebly opisthogyrate, set a little in front of the median vertical and well up above the dorsal margins; anterior and posterior dorsal slopes very gentle, the posterior a little more produced and not quite so low as the anterior ; anterior end well rounded, posterior end obscurely truncate; base line strongly and symmetrically arcuate; external surface sculptured with twenty-six to thirty-five angular radials, approximately uniform in size and spacing over the medial portion of the shell, separated by slightly wider concave interspaces; radials diminishing in prominence anteriorly but persistent almost to the margin, evanescing much more abruptly posteriorly, leav-
MARYLAND GEOLOGICAL SURVEY 637
ing the posterior sixth of the shell smooth; incremental sculpture over- running the radials and minutely nodulating them in the umbonal region, imbricating them away from the umbones ; characters of interior not known.
Liopistha protexia Conrad is abundant and widespread in the Upper Cretaceous of the East Coast and Gulf. For that reason and because its stratigraphic distribution is apparently restricted it has been used by Stephenson 1 as the guide fossil for the so-called Liopistha protexta sub- zone which he has traced through Georgia, Alabama and Mississippi.
Occurrence. — MONMOUTH FORMATION. Bohemia Mills, Cecil County; Millersville, Anne Arundel County; Brightseat, Brooks estate near Seat Pleasant, railroad cut 1 mile west of Seat Pleasant, 2 miles south of Oxon Hill, Prince George's County, Maryland. EANCOCAS FORMATION. Noxontown Pond, Delaware.
Collections. — Maryland Geological Survey, Philadelphia Academy of Natural Sciences, New Jersey Geological Survey, U. S. National Museum.
Outside Distribution. — Matawan Formation. ? Wenonah sand, New Jersey. Monmouth Formation. Navesink marl, Eed Bank sand and Tinton beds, New Jersey. Peedee Formation. North and South Caro- lina. Ripley Formation. Exogyra costata zone, Eufaula, Alabama; Chickasaw, Lee, Pontotoc, Union, Tippah and Alcorn counties, Mississippi. Extreme top of zone, Pataula Creek, Georgia; Chattahoochee River, Ala- bama. Selma Formation. Exogyra costata zone, Wilcox County, Ala- bama ; east-central Mississippi.
LIOPISTHA ALTERNATA Weller
Liopistha alternata Weller, 1907, Geol. Survey of New Jersey, Pal., vol. iv, p. 527, pi. Iviii, figs. 7-9.
Description. — " The dimensions of an average left valve are : Length 22 mm., height 15.5 mm., convexity 7 mm. Shell, exclusive of the pro- jecting beaks, subelliptical in outline. Beaks central, or in some speci- mens apparently a little back of the center, their apices pointed, elevated
1 Prof. Paper, U. S. Geol. Survey, No. 81.
638 SYSTEMATIC PALEONTOLOGY
above the hinge line, strongly incurved and nearly or quite in contact. Antero-cardinal slope slightly concave or nearly straight ; anterior margin rather sharply rounded ; basal margin broadly and regularly convex ; pos- terior margin rather sharply rounded above to the posterior extremity of the hinge line ; post-cardinal slope more concave than the anterior. Valves ventricose or inflated in the umbonal region, the surface curving abruptly to the cardinal margin, convex to the anterior and ventral margins, more or less compressed to the postero-cardinal extremity; slightly gaping pos- teriorly. Surface marked with forty or more angular, radiating costa? in adult shells, the alternate ones being conspicuously larger. The smaller costae are intercalated between the larger ones and do not reach the beak, so that in very young shells the alternation of costae does not exist ; upon the posterior, more or less compressed portion of the valves the costae are nearly or quite obsolete. Distinct impressions of the external surface of the shells show them to be marked by fine, indistinct lines of growth ; they also show each costa, both the larger ones and the smaller ones, to be surmounted by a row of fine tubercles or short spines, whose distance apart is less than the spaces between the costse; the radiating lines of tubercles are also present upon the posterior non-costate portion of the shell. This species can be easily distinguished from /,. profe.rta by the alternating costae and the more central position of the beaks. These two species have never been observed associated in the same fauna, /,. aHernata being characteristic of the Merchantville, while L. protexta is especially characteristic of the Navesink." — Weller, 1907.
The occurrence in Maryland is restricted to a single broken valve, but it is sufficient to show the diagnostic development of a secondary radial lineation.
Occurrence.— MATAWAN FORMATION. Summit Bridge, Chesapeake and Delaware Canal, Delaware.
Collections. — Maryland Geological Survey, New Jersey Geological Sur- vey, U. S. National Museum.
Outside Distribution. — Matawan Formation. Merchantville clay marl, New Jersey. Eutaw Formation (Tombigbee sand member). Exogyra ponderosa zone, Mortoniceras subzone, Georgia : Perry County. Alabama.
MARYLAND GEOLOGICAL SURVEY 639
Family CUSPIDAR1DAE
Genus CUSPIDARIA Nardo [Ann. Sci., Lombardo Veneto, vol. x, 1840, p. 49]
Ty/ic. — Tellina cuspidata Olivi.
Shell minutely pyriform in outline, feebly inequivalve, strongly inequi- lateral, the anterior portion of the shell inflated, the posterior abruptly constricted and compressed; squarely truncate, gaping.
" The shells of Cuspidaria possess an internal ligament, received in each valve in a more or less differentiated groove or fossette, which may project from the umbonal angle of the hinge margin, or be more or less adherent to the anterior or posterior slope of this angle. They may have one anterior and one posterior cardinal and lateral tooth in valve, any one of which (or all in the genus ? Myonera) may be entirely absent. Beside the teeth the hinge is reinforced in many cases by a buttress extending in a direction vertical to the valve from the hidden surface of the hinge margin, posterior to the umbonal angle. This buttress may consist of the vertical plate above mentioned and a thickened rib curving round in front of the posterior muscular scar, and then directed poste- riorly, becoming almost immediately obsolete. Or the posterior muscular insertion may be elongate and narrow, and the buttress take the form of a " clavicle " or myophore, elongated, parallel with the posterior hinge margin and separating the two posterior muscular scars. The muscles are not always inserted upon the buttress, but may be above and in front of it. Its purpose would seem to be that of strengthening the valve, almost always thin and fragile, against sudden contractions of the muscles, and to support the cardinal border, and especially the strong posterior lateral tooth found in many species. When this tooth is found in a species which has no posterior lateral in the other valve, the valve which has a tooth shows the buttress stronger than the other, indicating its function as a support for the tooth ; but when elongated and clavicular there is little difference between the buttresses of opposite valves, indicating that in such cases the function is the strengthening of the valve itself. The presence of the buttress is. in my opinion, important only in a minor degree, except
Etymology: Cuspis, cuspidis; a lance, a point.
640 SYSTEMATIC PALEONTOLOGY
when it takes the clavicular form, as, in different species of the same group, and even in individuals of the ^ame species, its size and prominence vary very greatly. Adriatic specimens of the typical species, C. cuspidata, show a strong buttress; British specimens of the same species often show it faintly or not at all, while otherwise well developed. The names Naera, Rhinomya, Aulacophora, Spathophora, and Trophidophora, among those which have been applied to members of this group, by Gray, Adams, and Jeffreys, are all preoccupied in zoological nomenclature, some of them several times over.
" The characters of radiating and concentric sculpture in this group have no more than a specific value ; there are few species where they tire not more or less combined in the external ornamentation. The surface may be polished, smooth, wrinkled, sulcate, or granulous. The anterior muscular scar is double or single, the posterior scar double, in all the specimens I have seen where the scars could be made out." — Dall, 1886. '
The genus was initiated in the Mesozoic and persists in the recent seas as one of the characteristic deep water forms. One species, C. lucifuga Fischer, has been reported from over 2500 fathoms.
A. Latitude of adult shell not exceeding 8 mm.; anterior portion of shell
not evenly inflated, tending to flatten toward the anterior lateral and ventral margins Cuspidaria ampulla
B. Latitude of adult shell exceeding 8 mm.; anterior portion of shell
evenly inflated, not flattened toward the anterior lateral and ventral margins Cuspidaria cucurbita
CUSPIDARIA AMPULLA n. sp. Plate XXXVII, Figs. 6, ?
Description. — Shell small, even for the genus, thin, approximately equivalve, strongly inequilateral, highly inflated in the umbonal region and the medial portion of the disk, flattening a little toward the anterior and ventral margins of the shell and abruptly compressed posteriorly; umbones inflated even to their apices, proximate, incurved, feebly opistho- gyrate, rising well above the dorsal margin, a little in front of the median horizontal; anterior dorsal margin steeply descending; posterior dorsal
1 Bull. Mus. Comp. Zool., Harvard Coll., 1886, p. 292.
MAEYLAND GEOLOGICAL SURVEY 641
margin feebly excavated ; anterior lateral margin rounding obliquely into the base; posterior very short and squarely truncate; base line smoothly convex in the anterior and medial portion, rapidly ascending and very feebly concave behind the median vertical ; external sculpture very feeble, little more, indeed, than irregular incremental striations; character of hinge and interior not known.
Dimensions. — Altitude 4.75 mm., latitude 6.75 mm., diameter, 4 mm.
It is separated from Cuspidaria cucurbita n. sp. by its smaller size and less produced and less evenly inflated anterior end. The type is unique.
Occurrence. — MONMOUTH FORMATION. Brightseat, Prince George's County.
Collection. — Maryland Geological Survey.
CUSPIDARIA CUCURBITA n. sp. Plate XXXVII, Figs. 4, 5
Description. — Shell of moderate size for the genus, oblique, minutely gourd-shaped; subequivalved, the right valve a little the more inflated; umbones gibbous, incurved, the apices proximate and opisthogyrate, placed a little behind the median horizontal; anterior dorsal margin gently sloping ; lateral margin obscurely truncate ; posterior portion of shell abruptly contracted and compressed, behind the umbones ; posterior dorsal margin feebly excavated, the short lateral margin squarely truncate ; base line arcuate in the anterior and medial portion, rapidly ascending pos- teriorly; characters of surface and interior not known.
Dimensions. — Altitude 7 mm., latitude 10.5 mm., maximum diameter of double valves 6 mm.
The cast of the double valves from which the shell is described suggests in its outline a miniature drinking gourd, the evenly inflated anterior and medial portion forming the cup, the abruptly constricted posterior por- tion the neck. The species is probably a close relative of Cuspidaria ven- tricosa Meek and Hayden, but it is much more oblique than the latter, and differs further in that the base line is not excavated at the rostrum. From Cuspidaria ampulla n. sp. it is separated not only by the larger size but
642 SYSTEMATIC PALEONTOLOGY
by the more produced and much more evenly inflated anterior portion of the shell.
Occurrence. — MATAWAN FORMATION. Three-quarters of a mile south- east of Ulmstead Point, Anne Arundel County.
Collection. — Maryland Geological Survey.
order TELEODESMACEA
Superfamily CYPR1CARDIACEA Family PLEUROPHORIDAE
Genus VENIELLA Stoliczka (Mem. Geol. Survey of India, Cret. Fauna S. India, 1871, vol. iii, p. 189)
= Venilia Morton 1833, Am. Jour. Sci., 1st ser., vol. xxiii, p. 294. Xot Venilia Dupouch 1829, a Lepidopteran genus.
Type. — Venilia conradi Morton.
" Shell ventricose, inflated, with the beaks outwardly incurved, more or less distant, a long narrow ligamental furrow running from them pos- teriorly, situated above strong fulcra; hinge with two cardinal and one posterior lateral tooth in each valve; right valve with the supra-posterior cardinal tooth, generally bifid anteriorly with a hook-like downward bent prolongation, infero-anterior cardinal smaller, lamelliform, or more or less tubercular, separated from the other tooth by a more or less horizontally extending flexuous groove into which the infero-anterior cardinal tooth of the left valve fits ; the supero-posterior cardinal of this valve is moder- ately prolonged, single or indistinctly bifid." — Stoliczka, 1871.
The shell is rude and heavy and, as a rule, subtrapezoidal or quadrate in outline with a more or less clearly differentiated lunule and escutcheon and an angulated posterior keel. Irregular concentric sculpture is usually developed, but it is rarely more than a modification of the heavy incre- mentals. The adductor impressions, particularly the anterior, are distinct or even excavated, as is so frequently the case in the heavy bivalves. The pallial line is entire.
The Cretaceous apparently marks the initiation and the culmination of Veniella, although it survived in diminished numbers into the Tertiary.
Etymology: A modification of Morton's pre-occupied Venilia, the name of one of the nymphs of Roman mythology.
MARYLAND GEOLOGICAL SURVEY 643
VENIELLA CONRADI (Morton) Stoliczka Plate XXXVIII, Figs. 2-7
Venilia conradi Morton, 1833, Am. Jour. Sci., 1st ser., xxiii, p. 294, pi.
viii, figs. 1, 2. Venilia conradi Morton, 1834, Syn. Org. Rem. Cret. Group, U. S., p. 67, pi.
viii, figs. 1, 2.
Venilia trigona Gabb, 1862, Proc. Acad. Nat. Sci., Phila., for 1861, p. 324. Venilia conradi Meek, 1864, Check List Inv. Fossils, N. A., Cret. and Jur.,
p. 13. Venilia trigona Meek, 1864, Check List Inv. Fossils, N. A., Cret. and Jur.,
p. 13.
Venilia conradi Conrad, 1868, Cook's Geol. of New Jersey, p. 727. Goniosoma inflata Conrad, 1869, Am. Jour. Conch., vol. v, p. 44, pi. i, fig. 10. Venilia elevata Conrad, 1870, Ibidem, vol. vi, p. 74, pi. iii, figs. 7, 7a. Veniella conradi Stoliczka, 1871, Mem. Geol. Survey of India, Pal., Cret.
Fauna Southern India, vol. iii, p. 190. Veniella conradi Meek, 1876, Kept. U. S. Geol. Survey, Territories, vol. ix, p.
148, text figures 9-11. Veniella conradi Whitfield, 1885, Mon. U. S. Geol. Survey, vol. ix, p. 144,
pi. xix, figs. 8-10.
Veniella trigona Whitfield, 1885, Ibidem, p. 149, pi. xix, figs. 11-14. Veniella inflata Whitfield, 1885, Ibidem, p. 147, pi. xix, figs. 4, 5. Veniella elevata Whitfield, 1885, Ibidem, p. 148, pi. xix, figs. 6, 7. Veniella conradi Johnson, 1905, Proc. Acad. Nat. Sci., Phila., p. 13. Veniella trigona Johnson, 1905, Ibidem. Veniella elevata Johnson, 1905, Ibidem. Veniella inflata Johnson, 1905, Ibidem. Veniella conradi Weller, 1907, Geol. Survey of New Jersey, Pal., vol. iv, p.
534, pi. Iviii, figs. 18, 19. Veniella trigona Weller, 1907, Ibidem, p. 537, pi. lix, figs. 1-3.
Description. — " Trigonal, ventricose, concentrically sulcated ; beaks long and incurved; diameter an inch and a half." — Morton, 1833.
Type Locality. — New Jersey.
Shell thick, heavy, prismatic, rudely cordate or trigonal in outline ; umbones very prominent, inflated to their very apices, which are turned inward and forward, and placed in the adult forms within the anterior third; posterior carina strongly denned, persisting from the umbones to the posterior ventral margin ; lunule very wide, differentiated by a faintly incised line and the evanescence of the heavy concentric sculpture; escutcheon suggested by an obscure keel running from the umbones to the extremity of the dorsal margin at a distance a little more than midway
644 SYSTEMATIC PALEONTOLOGY
between the posterior carina and the hinge margin ; escutcheon much more sharply denned in the young forms than in the adults ; anterior portion of shell smoothly rounded, even nasute in the young; base line approxi- mately horizontal; posterior dorsal and distal margins merging into one another in the adults, the lateral margin squarely truncate in the young ; external surface broadly corrugated in the umbonal region, the summits of the obtuse ridges thus formed crowned with sharp laminar plates uni- form in thickness throughout their extent, although the altitude attained sometimes approaches a centimeter; laminae often broken away leaving only a faint scar which is soon eradicated by exposure; the number of processes thus developed rarely exceeding five; ventral portion of adult shell evenly rounded and sculptured only with heavy growth lines and crowded resting stages; ligament external, opisthodetic, seated upon a short but rather stout nymph; hinge plate heavy, two cardinals in the right valve, the anterior trigonal and placed opposite the lateral, the pos- terior robust, obliquely elongated and compressed, feebly sulcated medially; a stout rounded anterior lateral tubercle developed on the ventral side of the hinge plate near the anterior cardinal ; posterior lateral grooved, profound, the inner surfaces finely striated transversely; two cardinals present also in the left valve, both of them posteriorly produced, the anterior stout and feebly sulcated, the posterior laminar and united with the basal margin ; anterior lateral sharp, trigonal with a deep pocket behind it for the reception of the corresponding lateral in the right valve ; posterior lateral elevated, produced; muscle impressions distinct, the anterior excavated ; pallial line entire.
The young of the species are subquadrate in outline and when fully armed present a very different aspect from the cordate adults from which the laminar plates have been broken away and all traces of them obliter- ated. However, all the changes in outline and sculpture may be observed in a single individual so that there is no doubt of the absolute identity of the V. conradi and V. trigona.
Even though there were, Morton's well-figured type is a fully adult form with all the characters of the individual described later by Gabb under the name of V. trigona.
MARYLAND GEOLOGICAL SURVEY 645
The species is unusually abundant and well preserved at Brightseat, Prince George's County.
Occurrence. — MAGOTHY FORMATION. ? Good Hope Hill, District of Columbia. MATAWAN FORMATION. Post 157, Chesapeake and Delaware Canal, Delaware; Ulmstead Point, Anne Arundel County, Maryland. MONMOUTH FORMATION. ? Millersville, Anne Arundel County; Bohemia Mills, right bank of Bohemia Creek near Scotchman's Creek, Cecil County ; east of mouth of Turner's Creek, Kent County ; Brightseat, railroad cut west of Seat Pleasant, Brooks estate near Seat Pleasant, 1 mile west of Friendly, McNeys Corners, Fort Washington, Prince George's County, Maryland.
Collections. — Maryland Geological Survey, Philadelphia Academy of Natural Sciences, New Jersey Geological Survey, U. S. National Museum.
Outside Distribution. — Matawan Formation. Merchantville clay marl, Wenonah sand, New Jersey. Monmouth Formation. Navesink marl, Eed Bank sand and Tiiiton beds, New Jersey. Black Creek Formation. North and South Carolina. Eutaw Formation (Tombigbee sand mem- ber) . Exogyra ponderosa zone, Mortoniceras subzone, Georgia ; Prentiss County, Mississippi. Transition beds, Eutaw to Selma. Exogyra pon- derosa zone, Mortoniceras subzone, Dallas County, Alabama. Ripley For- mation. Exogyra ponderosa zone, Barbour County, Alabama. Extreme top of zone, Pataula Creek, Georgia. Selma Formation. Exogyra pon- derosa zone, Lee County, Mississippi. Exogyra costata zone, Wilcox County, Alabama; east-central Mississippi.
Superfamily ASTARTACEA Family CRASSATELLITIDAE
Genus CRASSATELLINA Meek [Hayden, 2d Kept. Geol. Survey, Territories, 1871, p. 300]
Type. — Crassatellina oblonga Meek.
" Shell transversely trapezoidal, equivalve, inequilateral, with free margins closed and smooth within; hinge with two cardinal teeth, and one elongated anterior and one posterior lateral tooth in each valve;
Etymology: Diminutive of Crassatella.
646 SYSTEMATIC PALEONTOLOGY
anterior cardinal tooth of the left valve trigonal, and deeply emarginato below ; posterior very much compressed, oblique, and somewhat elongated ; cardinal teeth of right valve diverging, with a triangular pit between for the reception of the larger triangular tooth of the other valve; anterior one small, oblique, and connected at its upper end with the posterior extremity of the anterior lateral ; posterior larger, oblique, longitudinally furrowed,1 and perhaps emarginated below, while just behind and above it there is a narrow oblique slit, or pit, for the reception of the thin anterior cardinal of the other valve ; lateral teeth elongated parallel to the cardinal margins ; the anterior one of the right valve, and the posterior of the left, apparently continued so as to connect with the upper ends of the cardinal teeth ; ligament external ; pallial line simple.
" The typical species of this genus has the general external appearance of a Crassatella, from which genus, however, it is clearly removed by its hinge characters, though evidently belonging to the same family. Its muscular impressions are faintly defined, as is also the case with the pallial line, which latter, however, can be followed so far back as to leave little or no doubt that it is really simple. The larger trigonal cardinal tooth of the left valve is probably sometimes so deeply emarginate as to give it an A-shape."— Meek, 1876.2
Meek's belief in the identity of the two genera has been sustained by later paleontologists. There is no record of the group from other than Cretaceous strata.
CRASSATELLINA CAROLINENSIS (Conrad) Meek Etea carolinensis Conrad, 1875, Kerr's Geol. of North Carolina, App., p. 6,
pi. i, fig. 14. Crassatellina carolinensis Meek, 1876, Kept. U. S. Geol. Survey, Territories,
vol. ix, pp. 119, 120.
Etea carolinensis Johnson, 1905, Proc. Acad. Nat. Sci., Phila., p. 14. Etea carolinensis Weller, 1907, Geol. Survey of New Jersey, Pal., vol. iv,
p. 541, pi. lix, figs. 4-6.
Description. — " Shell suboval, short, equilateral, compressed, with dis- tinct lines of growth ; posterior end truncated, nearly direct." — Conrad, 1875.
1 The furrow of this tooth is too strongly defined in fig. 3d, of plate 2. 3 Kept. U. S. Geol. Survey, Territories, vol. ix, pp. 119, 120.
MARYLAND GEOLOGICAL SURVEY 647
Type Locality.— Snow Hill, North Carolina.
" The dimensions of a shell of average size, preserving both valves, are : Length 33 mm., height 22.5 mm., thickness 14 mm. Length of the largest individual observed, 14 mm. Shell very oblique and inequilateral, the beaks obtuse, slightly incurved, situated about three-eighths of the entire length of the shell from the anterior extremity. Anterior margin some- what narrowly rounded and passing into the basal margin ; basal margin moderately convex anteriorly, becoming straight or usually slightly con- cave posteriorly; posterior-basal extremity acutely angular; posterior margin rather short, obliquely truncate; postero-dorsal margin straight, except near the beak where it becomes slightly convex, making an angle of about 136° with the truncate posterior margin. Surface of the shell marked with a sharply angular or subcarinate, usually straight, umbonal ridge passing from the beak to the postero-basal extremity of the shell; postero-dorsal slope concave from the umbonal ridge to the cardinal mar- gin, where the shell is sharply inflected to form a large and nearly flat escutcheon ; in front of the umbonal ridge a broad, more or less indefinite depression passes from the beak to the sinuosity in the posterior portion of the ventral margin ; in front of the beak the surface is inflected to form a rather large and broad lunule. Entire surface of the shell covered with strong, concentric lines of growth which are more or less irregular in the strength of their development. Hinge of right valve with a large bifid cardinal tooth directed obliquely backwards from beneath the beak, and a much smaller simple one directed forward; between these two teeth is a deep triangular pit, and behind the posterior one is a much narrower pit ; two large lateral teeth are present, one in front and one behind the beak, the anterior one is nearer the beak with a broad and deep pit between it and the hinge line, the posterior one is more elongate and slender, and is also separated from the hinge line by a deep pit. The hinge of the left valve has two cardinal teeth, a large bifid one immediately beneath the beak and a thin, very oblique one behind, with a large, oblique, triangular pit between the two ; there are two strong lateral teeth, one in front and one behind, the anterior one being nearer the beak and usually stronger but not so much extended longitudinally as the posterior one. Muscular
648 SYSTEMATIC PALEONTOLOGY
impressions large and strong, of abdut equal size ; pallia! line parallel with the truncated posterior margin for a short distance below the posterior muscular impression, then bending abruptly forward and continuing sub- parallel with the shell margin." — Weller, 1907.
CrassatelUna carolinensis Conrad is represented in Maryland and Dela- ware by a single imperfect cast. The species is apparently one of the most reliable guide fossils of the Exogyra ponderosa zone.
Occurrence. — MATAWAN FORMATION. Post 105, Chesapeake and Dela- ware Canal, Delaware.
Collections. — Maryland Geological Survey, Philadelphia Academy of Natural Sciences, New Jersey Geological Survey, U. S. National Museum.
Outside Distribution. — Matawan Formation. Marshalltown clay marl, New Jersey. Black Creek Formation. North and South Carolina. Pcedee Formation. North and South Carolina. Eutaw Formation. Basal. Exogyra ponderosa zone, Eussell County, Alabama. (Tombigbee sand member). Mortoniceras subzone, Georgia; Eussell County, Ala- bama; Prentiss County, Mississippi. Eipley Formation. Exogyra pon- derosa zone, Barbour County, Alabama. Exogyra costata zone, Union County, Mississippi. Extreme top of zone, Pataula Creek, Georgia. Selma Formation. Exogyra costata zone, east-central Mississippi.
Genus CRASSATELL1TES Kriiger [Arch. Neuest. Entd. Urwelt, vol. ii, 1828, 4661
Type. — Crassatella gibbosula Lamarck.
" Shell solid, inequilateral, slightly inequivalve, usually subtrigonal, the posterior end longer ; valves closed, the ligament and resilium adjacent and internal ; hinge of three cardinals in the right valve, of which the pos- terior is more or less effaced by the resilium, and two in the left valve ; the anterior edge of the right and the posterior edge of the left hinge margin grooved to receive the edge of the opposite valve, which is bevelled to serve as a lateral lamina ; sculpture chiefly concentric and often obsolete except near the umbones." — Dall, 1903.1
Etymology: Crassus, thick, heavy.
1 Trans. Wagner Free Inst. Sci., Phila., vol. iii, pt. vi, pp. 1466, 1467.
MARYLAND GEOLOGICAL SURVEY 649
The genus originated, apparently, in the Cretaceous, culminated in the Tertiary, and is represented in the Recent faunas by some thirty or forty species confined, for the most part, to the tropical seas. In the East Coast and Gulf Eocene, and in the East Coast Miocene, the genus is one of the most prolific and conspicuous of any of the bivalves.
A. Outline ovate or ovate-trigonal, not conspicuously produced along the
posterior keel.
1. External surface incrementally sculptured but not more or less
regularly lineated from umbones to base.
a. Shell very heavy, especially in the umbonal region; posterior
carina usually prominent Crassatellites vadosus
b. Shell not very heavy and uniform in weight; posterior carina
not very prominent Crassatellites subplanus
2. External surface more or less regularly lineated from umbones
to base Crassatellites linteus
B. Outline alate, conspicuously produced along the posterior keel.
Crassatellites pteropsis
CRASSATELLITES VADOSUS (Morton) Johnson Plato XXXIX, Figs. 1-4
Crassatella vadosa Morton, 1834, Syn. Org. Rem. Cret. Group, U. S., p. 66,
pi. xiii, fig. 12. Crassatella ripleyana Conrad, 1858, Jour. Acad. Nat. Sci., Phila., 2d ser.,
vol. iii, p. 327, pi. xxxv, fig. 3. Crassatella vadosa Meek, 1864, Check List Inv. Foss., N. A., Cret. and Jur..
p. 11. Crassatella vadosa Stoliczka, 1871, Mem. Geol. Survey of India, Pal. Indica,
Cret. Faunas Southern India, vol. iii, p. 295.
Crassatella vadosa Gabb, 1876, Proc. Acad. Nat. Sci., Phila., p. 310. Crassatella vadosa Conrad, 1878, Cook's Geol. of New Jersey, p. 726. Crassatella vadosa "Whitfield, 1885, Mon. U. S. Geol. Survey, vol. ix, p. 116.
pi. xvii, figs. 12-15.
Crassatellites vadosus Johnson, 1905, Proc. Acad. Nat. Sci., Phila., p. 14. Crassatellites ripleyana Johnson, 1905, Ibidem. Crassatellites subplanus Weller, 1907, Geol. Survey of New Jersey, Pal., vol.
iv, p. 553 (ex parte), pi. Ixi, figs. 1, 2(?).
Description. — " Ovato-triangular, slightly compressed ; with about thirty distinct, concentric stria?. Length one inch and a quarter ; breadth one inch." — Morton, 1834.
Type Locality. — Prairie Bluff, Alabama.
Shell of medium size, thick, heavy, rudely trigonal in outline; anterior and lateral margins rounded, posterior more or less produced and trun-
650 SYSTEMATIC PALEONTOLOGY
cated, ventral margin approximately horizontal ; umbones orthogyrate or turned a little forward, proximate, often thickened, flattened upon their summits, placed back from the anterior margin a distance of one-third the total latitude; lunule broadly lenticular, sharply denned, the portion in the left valve a trifle broader and more feebly striated by the incrementals than that of the right; escutcheon more sharply defined, broader and a trifle larger in the right valve than in the left ; posterior area outlined by an obtuse ridge passing from the umbones to ths posterior ventral margin ; external surface sculptured with low, concentric ridges close set but irregular in arrangement, suggesting an exaggerated incremental sculp- ture ; a few pronounced resting stages, usually developed toward the ven- tral margin ; radial sculpture manifested only in the sharp denticulations on the inner margins ; hinge plate very heavy, ligament pit a small scoop- shaped affair, extending obliquely backward from directly beneath the tips of the umbones; cardinals two in number in the left valve, three in the right, the anterior cardinal of the right very thin and laminar, and fused at the base with the dorsal margin, the middle cardinal heavy, trigonal, transversely striated; the posterior cardinal laminar largely effaced by the resilium, originating near the base of the anterior cardinal and diverg- ing from it at an angle of approximately 60°, cardinals of the left valve much more nearly equal than those of the right, the posterior rather thin, just under the umbones where it forms the anterior margin of the ligament pit, but expanding rapidly toward its ventral extremity; left cardinals striated on their inner faces, separated by a deep trigonal pit for the reception of the right anterior cardinal ; small sulcus near the base of the left posterior cardinal provided for the laminar posterior cardinal of the right valve; no trace of true laterals developed but the posterior dorsal margin of the right valve and the anterior dorsal margin of left valve bevelled to function as laterals and received in grooves in the opposite valves; muscle impressions subequal, placed near the median horizontal, the anterior more deeply excavated than the posterior ; anterior pedal scar very distinct, set under the hinge plate a little dorsal to the anterior adductor; pallia! line entire; inner margins finely crenulated from the ventral extremity of the lunule to the ventral extremity of the escutcheon.
MAJIYLAXD GEOLOGICAL SURVEY G51
C. vadosus Morton shows a wide range of variation in age characters. The young are thin, rather compressed and truncated but not produced posteriorly ; with increasing age the form becomes apparently more inflated because of the umbonal thickening, and obliquely produced posteriorly. (Plate XXXII, Fig. 3.)
Conrad's C. ripleyana is doubtless a synonym, which includes the larger and heavier individuals. The young are quite uniform in outline and sculpture, but after the form has passed the typical C. vadosus stage there is a strong tendency for it to become produced posteriorly and to develop a rather heavy carina with the concomitant medial depression stage rep- resented by the (7. ripleyana. The species differs constantly from C. sub- planus in the heavier, less compressed and more inequilateral shell, the less prominnent keel and the much heavier and more trigonal hinge plate.
Although the species has not been reported from New Jersey it would be by no means surprising if the numerous casts from the Monmouth, which have been referred to C. subplanus Conrad, would find their true affinities with C. vadosus Morton, which is by far the most abundant rep- resentative of the genus in Maryland and constitutes, indeed, one of the major factors in the Monmouth fauna.
Occurrence. — MOXMOUTH FORMATIOX. ? Millersville, Anne Arundel County. Brightseat, railroad cut west of Seat Pleasant, Brooks estate near Seat Pleasant, Fort Washington, Prince George's County.
Collections. — Maryland Geological Survey, Philadelphia Academy of Natural Sciences, New Jersey Geological Survey, U. S. National Museum.
Outside Distribution. — Monmouth Formation. Navesink marl, and Tinton beds, New Jersey. Ripley Formation. Exogyra costata zone, Union and Tippah counties, Mississippi. Selma Formation. Exogyra costata zone, Wilcox County, Alabama; east-central Mississippi.
CRASSATELLITES SUBPLAXUS (Conrad) Johnson
Crassatella subplana Conrad, 1853, Jour. Acad. Nat. Sci.. Phila., 2d ser.,
vol. ii, p. 274, pi. xxiv, fig. 9. Crassatella subplana Meek, 1864, Check. List Inv. Foss., N. A. Cret. and
Jur., p. 11.
652 SYSTEMATIC PALEONTOLOGY
Crassatella subplana Whitfield, 1885, Mon. U. S. Geol. Survey, vol. ix, p.
121, pi. xviii, figs. 14-16.
Crassatellites subplanus Johnson, 1905, Proc. Acad. Nat. Sci., Phila., p. 14. Crassatellites subplanus Weller, 1907, Geol. Survey of New Jersey, Pal.,
vol. iv, p. 553 (ex parte, synonymy excluded.)
Description. — " Subtriangular, compressed or plano-convex ; anterior margin obtusely rounded ; posterior extremity subtruncated ; posterior basal margin straight or slightly contracted ; disk marked with numerous prominent acute concentric ridges and fine concentric lines." — Conrad, 1853.
Type Locality. — Arneytown, New Jersey.
" The dimensions of a small specimen, a nearly perfect right valve, are : Length 36 mm., height 28 mm., convexity 6 mm. Large individuals grow to a length of 50 mm. or more. Shell broadly subovate in outline, beak obtuse, situated about one-third the length of the shell from the anterior extremity. Antero-cardinal margin straight or slightly concave, sloping downward from the beak ; anterior margin rounding into the basal margin, moderately convex throughout to the postero-basal extremity, which is obtusely subangular ; posterior margin short, truncated nearly vertically or slightly inclined; postero-cardinal margin gently convex, sloping down- ward from the beak and meeting the posterior margin in an obtuse angle. Surface of the shell with an obtusely angular umbonal ridge, which passes from the beak to the postero-basal angle in nearly a straight line, the post- cardinal slope slightly concave to the cardinal margin ; the post-cardinal margin sharply inflected to form a rather deeply excavated escutcheon ; antero-cardinal margin inflected to form a deep but rather ill-defined lunule. Surface of the shell marked by regular, somewhat imbricating, concentric lines of growth, and often by a few broader concentric undula- tions towards the margin. Hinge of the right valve with a strong car- dinal tooth transversely striate on its anterior surface, directly beneath the beak. Behind it is a very large and broad triangular pit, with a much smaller secondary pit just behind the lower end of the tooth ; in front of the cardinal tooth is a small triangular pit about equal in size to the secondary pit behind, and in front of this pit a low, obscure, tooth-like ridge extends obliquely forward to the upper margin of the anterior mus-
MARYLAND GEOLOGICAL SURVEY 653
cular scar. Muscular impressions strong and about equal in size. Inner margin of the free edge of the shell crenate. The above description is based largely upon a very perfect right valve from the Marshalltown clay marl near Swedesboro." — Weller, 1907.
The species has a very meager representation in Maryland, and is, appa- rently restricted in its distribution to the Matawan. It differs from C. vadosus Morton, so prolific in the Monmouth of Maryland and the Gulf, in its more compressed valves, less anterior umbones, and much lighter shell, with the consequently thinner hinge plate and less pronounced pos- terior keel.
Occurrence. — MATAWAN FORMATION. Ulmstead Point, ? Arnold Point, Anne Arundel County.
Collections. — Maryland Geological Survey, Philadelphia Academy of Natural Sciences, New Jersey Geological Survey.
Outside Distribution. — Matawan Formation. Marshalltown clay marl, Wenonah sand, New Jersey. Monmouth Formation. ? Navesink marl, ? Eed Bank sand, ? Tinton beds, New Jersey.
CRASSATELLITES LINTEUS (Conrad) Johnson Plate XXXIX, Figs. 6, 7
Crassatella lintea Conrad, 1860, Jour. Acad. Nat. Sci., Phila., 2d ser., vol. iv, p. 279, pi. xlvi, fig. 5.
Crassatella lintea Meek, 1864, Check List Inv. Fossils, North America, Cret. and Jur., p. 11.
Crassatella lintea Conrad, 1868, Cook's Geol. of New Jersey, p. 726.
Crassatellites linteus Johnson, 1905, Proc. Acad. Nat. Sci., Phila., p. 14.
Crassatellites subplanus Weller, 1907, Geol. Survey of New Jersey, Pal., vol. iv, p. 553, pi. Ixi, figs. 3, 4 (ex parte, synonymy and figs. 1, 2 ex- cluded.)
Description. — " Subovate or subtriangular, convex, inequilateral ; disk concentrically ridged and finally striated, slightly contracted near the umbonal slope, which is rounded; posterior extremity subtruncated ; apex slightly prominent; posterior dorsal line nearly straight, very oblique; margin within finely crenulated; lunule long and lanceolate." — Conrad, 1860.
Type Locality. — Alabama.
654 SYSTEMATIC PALEONTOLOGY
Shell rather small for the genus and rather thin, compressed, subovate to ovate-trigonal in outline ; umbones rising a little above the dorsal mar- gin, their apices acute and prosogyrate, slightly anterior in position; lunule and escutcheon clearly differentiated but very narrow because of the compression of the valves; anterior end broadly and symmetrically rounded in front of the umbones; posterior dorsal margin gently sloping; lateral margin obscurely and obliquely truncate : base line rounding smoothly into the anterior lateral margin, obtusely angulated at the union with the posterior ; posterior keel obscure but persistent from the umbones to the posterior ventral margin, better defined by the change in the direc- tion of the growth lines than by any variation in the plane ; external sur- face sculptured with a very irregular concentric lineation, sharpest and most regular in the umbonal region, and occasional more or less accentu- ated growth lines and resting stages; ligament external, lodged beneath the umbones, the resilium buttressed ventrally by the posterior cardinal which it has largely effaced; medial right cardinal stout, trigonal, sub- umbonal, transversely striated laterally; anterior cardinal laminar; hinge dentition in left valve restricted to two subequal cardinals, the posterior a little the larger, both of them striated upon tbeir inner faces; no trace of laterals developed but anterior margin of left valve and posterior margin of right valve bevelled to function as laterals and received in shallow sockets in the corresponding valve ; muscle impressions distinct, impressed in the adults, placed high up at the distal extremities of the hinge ; pallial line simple, distinct, rather distant from the base line.
C. linteus Conrad has been considered, without justification, as the young of some of the clearly allied and larger forms, such as C. vadosus and C. subplanus. Aside from the fact that it shows no evidence of imma- turity, the shell is thinner and more compressed and much less strongly carinated posteriorly than C. vadosus of the same size. The resemblance to C. subplanus is more striking, but the concentric sculpture is finer and more sharply impressed in the former, and as a rule, the umbones are set farther forward and are more strongly prosogyrate.
C. linteus has a distribution in Maryland very similar to that of vadosus. but is very much less prolific.
MARYLAND GEOLOGICAL SURVEY 655
Occurrence. — MOXMOUTH FORMATION. Brightseat, Brooks estate near Seat Pleasant, Friendly, 1 mile west of Friendly, Fort Washington, Prince George's County.
Collections. — Maryland Geological Survey, Philadelphia Academy of Natural Sciences, Xew Jersey Geological Survey.
Outside Distribution. — Matawan Formation. Marshalltown clay marl, Wenonah sand, Xew Jersey. Monmouth Formation. Xavesink marl, Red Bank sand, Tinton beds, Xew Jersey.
CRASSATELLITES PTEROPSIS Conrad Plate XXXIX, Fig. 5
Crassatella pteropsis Conrad, 1860, Jour. Acad. Nat. Sci., Phila., 2d ser.,
vol. iv, p. 279, pi. xlvi, fig. 9.
Crassatella pteropsis Gabb, 1860, Ibidem, p. 395, pi. Ixviii, fig. 28. Crasatella pteropsis Meek, 1864, Check List Inv. Fossils N. A., Cret and Jur.,
p. 11. Crassatella (Pachythd'rus) pteropsis Conrad, 1869, Am. Jour. Conch., vol. v,
pp. 47, 48. Crassatella (Pachythtrrus) pteropsis Conrad, 1872, Proc. Acad. Nat. Sci.,
Phila., p. 50, pi. i, fig. 1. Crassatella pteropsis Gabb, 1876, Ibidem, p. 310.
Description. — " Aliform, very inequilateral, convex anteriorly, poste- riorly contracted ; umbonal slope slightly carinated below the umbo ; pos- terior side rostrated ; surface with minute concentric, impressed lines, very fine and closely arranged on the umbo and summit ; margin within finely crenulated." — Conrad, 1860.
Type Locality. — Owl Creek, Tippah County, Mississippi.
Shell rather thin and compressed, not very large, very inequilateral, posteriorly produced and alate in outline ; umbones flattened upon their summits, orthogyrate, proximate, set back from the anterior extremity a distance of approximately one-third the latitude; lunule and escutcheon sharply defined, narrowlv lenticular, subequal in size, the portion of the lunule in the right valve and of the escutcheon in the left valve shorter, narrower and more strongly sculptured incrementally than the corre-
656 SYSTEMATIC PALEONTOLOGY
spending portion in the opposite valve ; anterior end of the shell broadly rounded; posterior end obliquely produced along an obtuse keel which extends from the umbones to the posterior ventral margin ; area in front of the keel broadly and feebly depressed, area behind it obliquely flattened ; posterior dorsal margin evenly and steeply sloping to a point opposite the pallial line where it is obtusely truncated; ventral margin gently arcu- ate anteriorly, slightly constricted in front of the carina; external surface sculptured in the umbonal region with sharp concentric ridges, close set and regularly spaced, merging ventrally into an irregular incre- mental sculpture; posterior keel smooth excepting for faint incrementals and a few sharp ridges at the very apices of the umbones ; radial sculpture absent; hinge rather frail, three cardinals in the right valve, two in the left; a laminar anterior, a moderately robust medial and an exceedingly thin, laminar posterior cardinal in the right valve, subequal and moder- ately heavy anterior and medial cardinals in the left; inner cardinal faces transversely striated ; posterior dorsal margin of right valve and anterior dorsal margin of left valve bevelled to function as laterals, received in the opposite valve by corresponding grooves ; anterior and posterior muscle and pedal adductor scars distinct; pallial line entire; inner margins very finely crenate.
The species is conspicuous among all other representatives of the genus in the Upper Cretaceous of Maryland by reason of the alate outline and the sharp concentric sculpture in the umbonal region.
Occurrence. — MATAWAN FORMATION. Ulmstead Point, Anne Arundel County. MONMOUTH FORMATION. Brightseat, railroad cut west of Seat Pleasant, Brooks estate near Seat Pleasant, Friendly, 1 mile west of Friendly, 'McNeys Corners, Prince George's County.
Collections. — Maryland Geological Survey, U. S. National Museum.
Outside Distribution. — Black Creek Formation. North and South Carolina. Ripley Formation. Exogyra costata zone, Eufaula, Alabama ; Owl Creek, Tippah County, Mississippi. Extreme top of zone, Pataula Creek, Georgia; Chattahoochee River, Alabama.
MAEYLAND GEOLOGICAL SURVEY 657
Superfamily CARDITACEA Family CARDITIDAE
Genus VENERICARDIA Lamarck [Syst. des Anim. sans Vert., 1801, p. 123 J
Type. — Venericardia imlricata Lamarck.
Shell closed; rounded, trigonal or cordate; umbones anterior, prosogy- rate; lunule small but deep; escutcheon narrow and elongate; sculpture dominantly radial; ligament external, opisthodetic, parivincular ; hinge dentition in the right valve consisting of three oblique cardinals ; in the left valve of two; laterals of both valves absent or very feeble; muscle impressions strongly defined; pallial line entire; inner margins crenate.
The genus was initiated in the Cretaceous; the Eecent representatives are, for the most part, inhabitants of cooler waters.
VEXERICARDIA ? INTERMEDIA (Whitfield)
Cardita intermedia Whitfield, 1885, Mon. U. S. Geol. Survey, vol. ix, p. 209,
pi. xxviii, figs. 14, 15. Cardita intermedia Weller, 1907, Geol. Survey of New Jersey, Pal., vol. iv,
p. 565, pi. Ixii, figs. 6-8.
Description. — " Form of cast transversely elliptical, or transversely ovate, exclusive of the beaks, largest at the posterior end. Valves very ventricose, with strong projecting beaks, which in this condition are moderately distant. Hinge line arcuate. Anterior end narrowly rounded ; posterior end more broadly rounded; basal margin strongly curved, muscular scars on the cast small but distinct; margin of the cast showing indications of ten or twelve rather strong radiating ribs between the muscular scars. This is a very ventricose form, and has had strong, enrolled, subanterior beaks, which have been directed slightly upwards as well as forward."— Whitfield, 1885.
The form referred to this species is an inside cast to which a bit of the shell substance still adheres in the umbonal region. It seems a trifle more
Etymology: So-called because of a supposed combination of the characters of Venus and Cardium.
658 SYSTEMATIC PALEONTOLOGY
compressed than Whitfield'a type but this may be due merely to the con- ditions of preservation.
Occurrence. — RAXCOCAS FORMATION. South feeder Noxontown Pond, Delaware.
Collections. — Maryland Geological Survey, Columbia University.
Outside Distribution. — Eancocas Formation. ? Yincentown sand, Manasquan marl, Xew Jersey.
Superfamily LUCINACEA Family LUC1N1DAE
Genus MYRTAEA Turton [Conchy. Insul. Britt,, 1822, p. 133]
Type. — Venus spinifera Montagu.
" Shell elongate-oval or subrectangular, moderately convex or com- pressed, dorsal areas obsolete, the sculpture of the disk chiefly concentric and lamellar; the sculpture less pronounced in the middle of the disk and frequently exhibiting a serrate appearance when the lamellae cross the bounding carina of lunule or escutcheon ; internally with the left laterals usually obsolete and only one right cardinal tooth ; cardinals entire ; liga- ment and resilium deep-set but not internal; anterior adductor scar lucinoid but rather short ; inner margins entire.
" This group is paralleled in Pliacoicles by several others which want the anterior right cardinal in the adult, but in Myrtcea the single right car- dinal seems to be normal, while in the subdivisions of Phacoides its absence is due to degeneration during the growth of the individual or to the dynamic results of the inthrusting of the lunule, which occupies the space where the anterior cardinal would otherwise develop." — Dall, 1903.1
The genus is reported from strata as old as the Jurassic. There has been a tendency to indiscriminately assign all lucinoids to Lucina, and it is probable that the occurrence of Myrtcea in the Mesozoic strata has been underestimated.
'Trans. Wagner Free Inst. Sci., Phila., vol. iii, pt. v, p. 1357.
MARYLAND GEOLOGICAL SURVEY 659
STEPHEN SONI n. sp. Plate XXXIX, Figs. 10, 11
Description. — Shell small, equivalve, inequilateral, valves compressed transversely, oblong to subrectangular in outline; lunule narrow, elon- gated, distinctly impressed and further differentiated by the absence of surface sculpture; escutcheon not denned; umbones small, broadly but feebly inflated, the apices flattened, acute and prosogyrate, slightly over- topping the dorsal margin a little front of the median horizontal ; anterior dorsal margin slightly constricted and feebly excavated in front of the umbones ; posterior dorsal margin gently sloping ; anterior lateral margin broadly arcuate, the posterior widely truncate ; base line feebly convex ; external surface sculptured with fine crowded, closely over-lapping con- centric lamella, attached along their ventral margins, the dorsal margins free and slightly raised near the anterior and posterior extremities of the shell ; ligament submarginal, opisthodetic ; hinge armature rather feeble, a single triangular cardinal in the right valve ; posterior cardinal and ante- rior and posterior laterals obsolete; left valve armed with two slender, divergent cardinals, the laterals appearing as short, incipient laminar proc- esses near the distal extremities of the hinge plate; muscle scars unequal, the anterior elongated, the posterior smaller and irregular in outline ; pallial line simple, distinct.
Dimensions. — Altitude 6.5 mm., latitude 7 mm., semi-diameter 2 mm.
Type Locality. — One mile west of Friendly, Prince George's County.
Named in honor of Dr. L. W. Stephenson of the U. S. Geological Survey.
Occurrence. — Mox MOUTH FORMATION. Brightseat, Brooks estate near Seat Pleasant, 1 mile west of Friendly, Prince George's County.
Collection. — Maryland Geological Survey.
Genus PHACOIDES Blainville [Manual Malacology, vol. i, 1825, p. 550]
Type. — Lucina jamaicensis Lam.
Shell more or less lenticular; compressed, as a rule, or slightly tumid; umbones low, subcentral, erect or prosogyrate; sculpture dominantly con-
Etymology: 0a/c6s, lentil; ei'5-s. like.
660 SYSTEMATIC PALEONTOLOGY
centric; anterior and posterior dorsal areas usually differentiated; luiiule frequently profound; escutcheon obsolete; ligament external, often deeply sunken; normal dentition of right valve consisting of a simple anterior cardinal, a bifid posterior cardinal and anterior and posterior laterals; normal dentition of left valve consisting of a bifid anterior cardinal, a simple posterior cardinal, and anterior and posterior lateral grooves; laterals and less frequently the cardinals often obsolete; muscle impres- sions strongly marked, the anterior elongate, the posterior oval ; inner margins smooth or crenulated ; pallial line entire.
The genus is abundantly represented in the Tertiaries, the Mesozoic, and, if it be made to include the Prolucina of Ball, may be traced as far back as the Silurian. The living species number more than one hundred, and though they are most prolific in the tropics, they are present in the temperate seas as well.
PHACOIDES NOXONTOWXENSIS n. sp. Plate XXXIX, Figs. 8, 9
Description. — Shell of moderate size, compressed, subcircular ; umbones nearly central, acute, prosogyrate, not very prominent, dorsal slopes gentle, the anterior a little less so than the posterior; lateral margins broadly rounded; base line strongly and symmetrically arcuate; external surface sculptured with acutely elevated concentric lamina?, regularly spaced, probably about twenty-five in number, and between them very faint secondary striations; ligament external, opisthodetic, lodged in a mar- ginal groove elongated parallel to the dorsal margin; dentition obscure, but two small diverging cardinals are distinctly present in each valve; laterals apparently not developed; character of muscle scars and pallial line not known.
Dimensions. — Altitude 26 mm., latitude 26±mm., diameter 3.5 mm.
This species is another of those Rancocas bivalves represented by abundant fragments. The concentric sculpture is so well characterized, however, that even a scrap showing the regularly arranged, acutely ele- vated laminae is recognizable. As the species constitutes so important a factor in the Rancocas fauna it does not seem wise to disregard it alto- gether, even though the material is so ill-preserved.
MARYLAND GEOLOGICAL SURVEY 661
Occurrence. — KANCOCAS FORMATION. South feeder ISToxontown Pond, Delaware.
Collection.— Maryland Geological Survey.
Genus TENEA Conrad [Am. Jour. Conch., vol. vi, 1870, p. 72]
Type. — Tenea parilis Conrad.
" A V-shaped tooth under the apex of the left valve,the anterior lobe of which is continued along the margin anteriorly, forming a long, deep pit above it; one distant very oblique cardinal tooth posterior to the apex. Hight valve: Two cardinal teeth united above; anterior one falcate, with a pit on each side ; posterior one curved and directed obliquely backward." —Conrad, 1870.
The genus in its known distribution is confined to the Cretaceous.
TENEA PARILIS Conrad
Mysia (Diplodonte) parilis Conrad, 1860, Jour. Acad. Nat. Sci., Phila., 2d
ser., vol. iv, p. 278, pi. xlvi, fig. 16.
Tenea parilis Conrad, 1870, Am. Jour. Conch., vol. vi, p. 73, pi. iii, fig. 12. Tenea parilis Conrad, 1875, Kerr's Geol. of North Carolina, App., p. 8, pi. ii,
fig. 25. Tenea parilis Tryon, 1884, Syst. and Struct. Conch., vol. iii, p. 216, pi. cxix,
fig. 72. Dosinia gabbi Whitfield, 1885, Mon. U. S. Geol. Survey, vol. ix, p. 161, pi.
xxii, figs. 4, 5. Tenea pinguis Whitfield, 1885, Mon. U. S. Geol. Survey, vol. ix, p. 163, pi.
xxii, figs. 1, 2 (not T. pinguis Conrad).
Tenea parilis Johnson, 1905, Proc. Acad. Nat. Sci., Phila., p. 15. Tenea parilis Weller, 1907, Geol. Survey of New Jersey, Pal., vol. iv, p. 572,
pi. Ixiii, figs. 1-6.
Description. — " Shell suborbicular, equilateral, ventricose, direct ; sur- face entire ; hinge- with the anterior cardinal channel very profound."- Conrad, 1860.
Type Locality. — Tippah County, Mississippi.
Shell thin, fragile, ovate in outline, moderately convex, slightly inequi- lateral, lunule and escutcheon not defined ; umbones inflated to their very
Etymology: Corruption of tenuis, thin.
662 SYSTEMATIC PALEONTOLOGY
apices, proximate, incurved and prosogyrate, placed a little in front of the median vertical ; anterior and ventral margins well rounded, merging gradually into one another, the outline of the posterior margin sometimes rounded, sometimes obscurely truncate obliquely ; external surface smooth excepting for faint incremental striations which are least feeble near the posterior extremity; ligament opisthodetic, lodged in a submarginal groove extending backward for some distance from the tips of the umbones ; hinge plate narrow, very fragile ; armature in the right valve consisting of a thin, laminar, hook-shaped cardinal directly beneath the umbones, its posterior arm vertically directed, its anterior arm approxi- mately horizontal ; right posterior cardinal slender, laminar, obliquely elongated, parallel to the dorsal margin ; anterior lateral developed as a thin plate proximate to and directly facing the anterior portion of the hooked cardinal; hinge of left valve consisting of an anterior A -shaped cardinal which fits between the left anterior lateral and the vertical arm of the cardinal hook of the right valve; a very thin, laminar, medial cardinal which is accommodated between the anterior lateral and the horizontal arm of the hook, and a thin, laminar, obliquely elongated, posterior car- dinal; muscle scars small, not very distinct, placed high up near the distal extremities of the dorsal margins ; pallial sinus narrow, but quite deep, steeply ascending; inner margins simple.
This species occurs very abundantly in the form of casts in the Mon- mouth of Prince George's County, but the shell is so exceedingly thin and so readily flaked off that it is seldom possible to secure a perfect indi- vidual.
Occurrence. — MAGOTHY FORMATION. Good Hope Hill, District of Columbia. MAT AW AX FORMATION. Post 105, Chesapeake and Delaware Canal, Delaware; ? Ulmstead Point, Anne Arundel County, Maryland. MONMOUTH FORMATION. Fredericktown, Cecil County ; Brightseat, Brooks estate near Seat Pleasant, McNeys Corners, Friendly, 2 miles south of 0-xon Hill, ? Fort Washington, Prince George's County, Maryland.
Collections. — Maryland Geological Survey, Philadelphia Academy of Natural Sciences, Xew Jersey Geological Survey.
MARYLAND GEOLOGICAL SURVEY 663
Outside Dixtrilmlion. — 'Magothy Formation. Cliffwood clay, Xew Jersey. Mataican Formation. Merchantville clay marl, Woodbury clay, Wenonah sand, Xew Jersey. Monmouth Formation. Xavesink marl, Eed Bank sand, Tinton beds, Xew Jersey.
Superfamily CARDIACEA Family CARDIIDAE
Genus CARDIUM Linne [Systema Naturae, ed. x, 1758, p. 678]
Type. — Cardium costatum Linne.
Shell usually subequilateral, closed, or slightly gaping, globose, the united valves subcordate laterally; umbones prominent, almost straight or with a slight anterior twist ; true lunule and escutcheon absent ; sculp- ture dominantly radial ; ribs often granulose, spinose or imbricated ; orna- mentation of lateral areas particularly of the posterior, often differing from that of the disk; ligament external, opisthodetic ; hinge character- ized, with a few exceptions, by two cardinals, of which the ventral is the stronger, and one of two posterior and one of two anterior lateral lamella? in each valve; cardinals more or less twisted; muscle impressions sub- equal; pallial line simple or slightly sinuous posteriorly: internal basal margins serrate.
The cardiums form a conspicuous element in the faunas of Cretaceous and Tertiary. They are rather fragile, as a rule, and not well adapted to preservation. The external sculpture is frequently formed from a super- ficial shelly layer which readily breaks away leaving no scar upon the polished surface beneath. For this reason it is difficult to tell when one is dealing with a perfectly fresh specimen. The recent representatives, the so-called cockles, number about two hundred species and are most abund- ant in the warmer waters.
A. External sculpture not spinose.
1. Altitude of adult shell not exceeding 40 mm.; posterior area flat-
tened; margins sharply serrate Cardium eufalensc
2. Altitude of adult shell exceeding 40 mm.; posterior area not flat-
tened; margins not sharply serrate Cardium spillmani
Etymology: Kapdia, heart.
664 SYSTEMATIC PALEONTOLOGY
B. External sculpture spinose; margins not serrate.
1. Altitude and latitude approximately equal; outline subequilat-
eral Cardium dumosum
2. Altitude greater than the latitude; outline inequilateral.
a. Anterior abductor muscle scar inconspicuous or obscure.
Cardium tenuistriatum
b. Anterior abductor muscle scar conspicuous .... Cardium kiimmeli
CARDIUM EUFALENSE Conrad Plate XL, Figs. 1, 2
Cardium eufalense Conrad, 1860, Jour. Acad. Nat. Sci., Phila., 2d ser., vol.
iv, p. 282, pi. xlvi, fig. 13. Cardium eufalense Meek, 1864, Check List Inv. Fossils, North America,
Cret. and Jur., p. 12. Cardium (Trachycardium) eufalense Conrad, 1868, Cook's Geol. of New
Jersey, p. 726. Cardium (Trachycardium) eufalense Gabb, 1876, Proc. Acad. Nat. Sci.,
Phila., p. 310. Not Cardium eufalense Whitfield, 1885, Mon. U. S. Geol. Survey, vol. ix,
p. 132, pi. xx, figs. 17-19. Cardium eufalense Weller, 1907, Geol. Survey of New Jersey, Pal., vol. iv,
p. 577, pi. Ixiii, figs. 17-20.
Description. — " Obliquely ovate, rather thick in substance, profoundly ventricose; ribs about thirty-eight, smooth, prominent, acutely rounded, on the posterior slope angular, compressed or carinated ; summit promi- nent; beaks contiguous." — Conrad, 1860.
Type Locality. — Eufaula, Alabama.
Shell rather small for the genus, obliquely cordate in outline, inflated, the maximum diameter above the median horizontal ; umbones tumid, ele- vated above the dorsal margin, the apices incurved and feebly prosogy- rate, subcentral in position ; dorsal margins approximately straight, the posterior slightly more pronounced than the anterior; anterior lateral margin obscurely truncate, rounding rather abruptly into the dorsal mar- gin and much more broadly into the ventral ; posterior area conspicuously flattened, the lateral margin squarely truncate; base line obliquely arcu- ate ; external surface sculptured with thirty-five to forty vigorous radials, crowded and inclined to be flattened upon their summits in the umbonal region, V-shaped and separated by interspaces of approximately equal width toward the ventral margins; costse twelve to fourteen in number
MARYLAND GEOLOGICAL SURVEY 665
upon the posterior slope, narrower and more distinctly spaced than upon the anterior and medial portions ; incremental sculpture obscure, except- ing for an occasional resting stage near the umbonal margin; ligament external, opisthodetic, mounted on short, thickened nymphs; cardinals two in number in each valve, the anterior very stout and conical, springing from directly beneath the umbones, the posterior mere tubercles at the extremities of the nymphs; short but prominent anterior and posterior laterals developed in the left valve, a double anterior and a single posterior in the right; muscle scars rather indistinct placed high up near the extremities of the dorsal margins, the posterior somewhat elongated ; pal- lial line obscure, ventral and lateral margins sharply serrate.
This species is the. most abundant representative of its genus within the area under discussion. It is rather smaller than the co-existing species and is best characterized by the flattening of the posterior portion of the shell and the truncation of the posterior lateral margin. The costals are somewhat tubular in structure so that when the outer layer of the shell surface is removed, as it frequently is by weathering, the inter- costal areas appear as flat-topped elevations separated by concave depres- sions.
Occurrence. — MAGOTHY FORMATION. Good Hope Hill, District of Columbia. MATAWAN FORMATION. ? Post 105, Chesapeake and Dela- ware Canal, Delaware; three-quarters of a mile southeast of Ulmstead Point, Ulmstead Point, Gibson's Island, north shore Round Bay, Severn River, Anne Arundel County, Maryland. MONMOUTH FORMATION. Bohemia Mills, Fredericktown, Cecil County; Brightseat, Brooks estate near Seat Pleasant, Friendly, 1 mile west of Friendly, McNeys Corners, Prince George's County, Maryland.
Collections. — Maryland Geological Survey, New Jersey Geological Sur- vey, IT. S. National Museum.
Outside Distribution. — MataiL-an Formation. Wenonah sand, New Jersey. Blade Creel: Formation. North and South Carolina. Eutaw Formation (Tombigbee sand member). Exogyra ponderosa zone, Mor- toniceras subzone, Blufftown, Georgia. Ripley Formation. Exogyra pon- derosa zone, Georgia : Barbour County, Alabama. Exogyra costata zone,
666 SYSTEMATIC PALEONTOLOGY
Georgia ; Eufaula, Alabama ; Union and Tippah counties, Mississippi. Extreme top of zone, Pataula Creek, Georgia; Chattahoochee River, Ala- bama.
C AUDI I'M SPILLMAXI Conrad
Cardium (Leevicardium) spillmani Conrad, 1858, Jour. Acad. Nat. Sci., Phila.,
2d ser., vol. iii, p. 326, pi. xxxiv, fig. 3. Cardium (Liocardium) spillmani Meek, 1864, Check List Inv. Fossils N. A.,
Cret. and Jur., p. 13. Cardium (Protocardium) perelongatum Whitfield, 1885, Mon. U. S. Geol.
Survey, vol. ix, p. 136, pi. xx, figs. 20-22; pi. xxi, figs. 4, 5. Pachycardium burlingtonense Whitfield, 1885, Ibidem, p. 138, pi. xxi, figs. 6, 7. Cardium (Lcevicardium) perelongatum Johnson, 1905, Proc. Acad. Nat. Sci.,
Phila., p. 15.
Cardium (Lcevicardium) burlingtonense Johnson, 1905, Ibidem, p. 15. Cardium (Lcevicardium) spillmani Johnson, 1905, Ibidem, p. 15. Cardium spillmani Weller, 1907, Geol. Survey of New Jersey, Pal., vol. iv,
p. 583, pi. Ixiv, figs. 9-11.
Description. — " Oblong or profoundly elevated, inequilateral, pro- foundly ventricose ; umbo and summit elevated ; beaks nearly contiguous ; surface with distant irregular grooves on the anterior side, and three to five radiating slightly impressed furrows on the umbonal slope." — Conrad. 1858.
Type Locality. — Owl Creek, Tippah County, Mississippi.
" The dimensions of a nearly perfect internal cast are : Height 87 mm., width 55 mm., thickness 60 mm. Shell more or less narrowly subovate in lateral view, and cordate in end view. Hinge line rather short, arched, extending further downward in front than behind ; anterior margin con- vex, the curvature becoming greater below; basal margin regularly rounded; posterior margin longer and straighter than the anterior, usu- ally slightly convex, sometimes straight or slightly sinuate in the casts a little above the middle. Beaks situated back of the middle of the hinge line, strongly elevated above it in the casts, pointed, incurved, and dis- tinctly curved forward. Umbones prominent, the most prominent portion of the shell being in an oblique line from the beaks to the postero-basal margin, this umbonal prominence being not at all angular. The posterior slope much more abrupt than the anterior, its surface conspicuously
MARYLAND GEOLOGICAL SURVEY 667
impressed above the middle of the shell about half-way between the top of the umbonal prominence and the posterior cardinal extremity. Muscular impressions large, the anterior ones deeply impressed, the pos- terior ones scarcely or not at all differentiated from the surface of the casts. The left valve with two strong cardinal teeth beneath the beak with a pit between, right valve with a single cardinal tooth; anterior lateral teeth more remote from the cardinal teeth than the posterior ones, and also apparently much stronger. Inner free margin of the valves crenate along the posterior margin, smooth along the basal and anterior margins. Sur- face of the shell marked by radiating ribs upon the posterior slope, which in the internal casts at least, continue only from the margin up to the umbonal prominence; central and anterior portions of the shell marked by concentric lines of growth only. Both of the species described by Whit- field from New Jersey as Cardium perelongatum and Pachycardium bur- lingtonense, are certainly internal casts of the shell described by Conrad from Mississippi as Cardium spillmani, the example to which the last two names was applied being an exceptionally broad specimen. The species is for the most part restricted to the Navesink marl, where it attains its maximum size. The specimens which have been rarely noticed in the Merchantville clay are usually small, although Whitfield's P. burling- tonense is a very large example." — Weller, 1907.
The species is represented in Maryland merely by imperfect casts, one of which must have been, when perfect, fully 115 mm. in altitude.
Occurrence. — MATAWAN FORMATION. Post 105, Chesapeake and Dela- ware Canal, Delaware. MONMOUTH FORMATION. Bohemia Mills, Great Bohemia Creek, 1 mile southeast of Bohemia Mills, right bank of Bohemia Creek between Scotchman's Creek and Bohemia Ferry Bridge, Cecil County, Maryland.
Collections. — Maryland Geological Survey, Philadelphia Academy of Natural Sciences, New Jersey Geological Survey, U. S. National Museum.
Outside Distribution. — Matawan Formation. Merchantville clay marl,
New Jersey. Monmouth Formation. Navesink marl, New Jersey. Black
Creek Formation. North and South Carolina. Peedee Formation.
North and South Carolina. Eutaw Formation (Tombigbee sand mem-
44
G68 SYSTEMATIC PALEONTOLOGY
her). Exogyra ponderosa zone, Mortoniceras subzone, Blufftown, Geor- gia; Prentiss County, Mississippi. Ripley Formation. Exogyra costata zone, Georgia; Eufaula, Alabama; Lee, Union and Tippah counties, Mis- sissippi. Extreme top of zone, Pataula Creek, Georgia. Selma Forma- tion. Exogyra costata zone, Wilcox County, Alabama; east-central Mis- sissippi.
CAEDIUM DUMOSUM Conrad
Cardium (Criocardium) dumosum Conrad, 1870, Am. Jour. Conch., vol. vi,
p. 75. Cardium (Criocardium) dumosum Whitfleld, 1885, Mon. U. S. Geol. Survey,
vol. ix, p. 133, pi. xx, figs. 9 and ? 13 (not figs. 10-12). Cardium dumosum Johnson, 1905, Proc. Acad. Nat. Sci., Phila., p. 15. Cardium dumosum Weller, 1907, Geol. Survey of New Jersey, Pal., vol. iv,
p. 590, pi. Ixv, figs. 7-10.
Description. — " Cordate equilateral, ventricose ; umbo broad ; summit very prominent; ribs very numerous, small, closely arranged, convex; interstices furnished with numerous long slender spines ; posterior mar- gin subtruncated or slightly convex ; height 1-J inch ; length the same."- Conrad, 1870.
Type Locality. — Haddonfield, New Jersey.
The spinose cardiums, C. Jciimmeli Weller, C. dumosum Conrad and C. tenuistriatum Whitfield, are represented in Maryland merely by casts of the interior or fragments of casts of the exterior. Weller has admirably differentiated the three species from material in a better state of preserva- tion than any available from Maryland, and his diagnoses have been quoted at considerable length.
" The dimensions of a large individual are : Height 18 mm., width 18 mm., convexity of one valve 6 mm. Shell subcircular in outline, but slightly inequilateral, moderately convex. Beaks situated at about the middle of the hinge line, rather small and incurved ; umbones prominent, the anterior and posterior cardinal slopes about equally steep ; shell slightly compressed at both cardinal extremities. Surface of the shell marked with about fifty-four rounded radiating costa?, with interspaces of about equal width; from the bottom of every third interspace on the central portion of the shell there arises a row of laterally flattened spines 1 to
MARYLAND GEOLOGICAL SURVEY 669
2 mm. in length, their distance apart being about equal to the space occupied by two costas; the two intervening interspaces are occupied by rows of much smaller tubercles a little compressed laterally, situated at intervals about one-third the distance between the spines in each row. On the anterior and posterior slopes of the shell several rows of spines alternate with single rows of tubercles. The longest spines occur upon the posterior cardinal slope."— Weller, 1907.
The species is represented in Maryland chiefly by casts of the interior, although a few fragments of the exterior surface have been preserved both in the form of casts and of the original shell. The casts are isloated from those of C. kummeli and C. tenuistriatum Whitfield by their rela- tively broader, more globose and much more nearly equilateral outline. It is by far the most abundant of the three species within the area under discussion.
Occurrence. — MATAWAN FORMATION. ? Post 105, Chesapeake and Delaware Canal, Delaware. MONMOUTH FORMATION. Brightseat, Brooks estate near Seat Pleasant, 2 miles southwest of Oxon Hill, Prince George's County, Maryland.
Collections. — Maryland Geological Survey, Philadelphia Academy of Natural Sciences, U. S. National Museum.
Outside Distribution. — Matawan Formation. Woodbury clay, Weno- nah sand, New Jersey. Monmouth Formation. Eed Bank sand, New Jersey. Eutaw Formation (Tombigbee sand member). Exogyra pon~ derosa zone, Prentiss County, Mississippi. Ripley Formation. Exogyra costata zone, Union and Tippah counties, Mississippi.
CARDIUM TENUISTRIATUM (Whitfield) Weller
Cardium eufalensis Whitfield, 1885, Mon. U. S. Geol. Survey, vol. ix, p. 132,
pi. xx, figs. 18, 19 (not fig. 17). (Not C. eufalense Conrad, 1860.) Cardium (Criocardium) dumosum Whitfield, 1885, Ibidem, p. 133, pi. xx,
figs. 10-12 (not figs. 9 and ? 13). (Not C. dumosum Conrad, 1870.) Cardium (Criocardium) multiradiatum Whitfield, 1885, Ibidem, p. 135, pi.
xxi, figs. 1-3. (Not C. multiradiatum Gabb, 1860.)
Fragum tenuistriatum Whitfield, 1885, Ibidem, p. 139, pi. xx, figs. 15, 16. Cardium tenuistriatum Weller, 1907, Geol. Survey of New Jersey, Pal., vol.
iv, p. 591, pi. Ixv, figs. 13-19.
670 SYSTEMATIC PALEONTOLOGY
Description. — " Shell below a medium size, irregularly trapezoidal or subtriangular in outline, highly ventricose and sharply angular along the posterior umbonal ridge, with a nearly vertical postero-cardinal slope. Beaks large, prominent and attenuated, projecting considerably above the hinge line. Anterior side of the shell short and regularly rounded ; pos- terior vertically truncate and the basal line oblique, being prolonged below toward the posterior umbonal angle. Surface marked, on the body of the shell at least, by very fine, semi-obsolete, radiating striae, the pos- terior cardinal slope not showing evidences of striations on the cast, the only condition under which it has been observed. Hinge features unknown.
" The shell has all the generic features of the genus Fragum, as far as can be determined from the external form, while the striations of the sur- face are much finer than is usually the case; but no ornamentation can be detected on the striations, and the features of the hinge are not visible. It is the only form of similar character yet known to me in the formations of the state."— Whitfield, 1885.
Type, Locality.— Marlborough, New Jersey.
"The dimensions of an internal cast are: Height 44 mm., width 37 mm., thickness 35 mm. Large examples sometimes attain a height of over 60 mm. Shell irregularly subovate in lateral view and cordate in end view. Hinge line arcuate; anterior and basal margins, from the extremity of the hinge line to the middle of the basal margin, describing a nearly regular, arcuate curve; postero-basal margin curving more sharply around the postero-basal extremity of the shell into the posterior margin; posterior margin -much straighter than the anterior, usually gently convex but sometimes nearly or quite straight. Beaks situated at about the middle of the hinge line, rather prominent, elevated, pointed and incurved, considerably more prominent in the casts than in the speci- mens with the shell preserved. Valves gibbous, most prominent, but not angular, along a line from the beaks to the postero-basal extremity, the posterior slope more abrupt than the anterior. Muscular impressions rather large, the posterior one scarcely impressed and often scarcely dis-
MARYLAND GEOLOGICAL SURVEY 671
tinguishable upon the casts; the anterior ones more strongly impressed. Each valve with a strong, somewhat curved cardinal tooth beneath the beak, with a pit for the reception of the tooth of the opposite valve ; in each valve is a single anterior and posterior, rather strong, lateral tooth, some- what remote but nearly equidistant from the cardinal tooth. The inner free margin of the valves is crenate. Externally the shell is marked by flat, radiating costs wider than the interspaces; from the interspaces rise rows of laterally compressed spinules or tubercles which are longer and stronger upon the anterior and posterior slopes towards the hinge extrem- ities ; on the central portion of the shell each third row of processes is more conspicuous than the two intervening rows, the spines being longer and larger, one of them occupying the space of two or three of the smaller ones of the intervening rows, the smaller ones sometimes being scarcely more than tubercles but little elevated above the surface of the ribs of the shell ; upon the anterior and posterior slopes of the shell the rows of larger and smaller spines alternate, there being but a single row of smaller spines between the larger ones.
" This species is by far the commonest and most widely distributed Cardium in the Cretaceous faunas of Xew Jersey. It exhibits considerable variation, especially in the straightness of the posterior margin of the shell and in the prominence of the postero-basal extremity, but the casts can almost always be easily recognized by the strong convexity or gib- bosity of the valves, and the abrupt posterior slope as compared with the anterior. The surface markings of the shell most closely resemble those of G. dumosum, but the radiating costfe are comparatively broader and natter with narrower interspaces, and consequently the spines upon the surface are more compressed laterally. C. dumosum is also more nearly equilateral, with less convex valves than this species, and does not attain so large a size.
" It has been a matter of much difficulty to determine to what species this common shell should be referred. Previous to the publication of Whitfield's monograph it seems usually to have been referred to C. multi- radiatum, or to G. eufalense. Whitfield has apparently illustrated dif-
672 SYSTEMATIC PALEONTOLOGY
fcrent individual internal casts of the species under four different spe- cific heads. His figures 18 and 19 of C. eufalense represent a more than usually gibbous cast of this species, the true C. eufalense being a fundamentally different shell without the spines rising from the inter- spaces between the ribs, and consequently not even a member of the sub- genus Criocardium. Whitfield' s figures 10 and 11 of C. dumosum repre- sent a more than usually rounded form of the species under discussion, the specimen is larger, more convex and has a steeper posterior slope than the true C. dumosum. Figure 12 of the same author, an enlargement to illustrate the surface characters of C. dumosum, also proves, upon exami- nation of the specimen, to be taken from a member of the species under consideration; the illustration is not an accurate representation of the characters of the specimen, the costse being too narrow, the interspaces too wide, and the spines not enough compressed laterally. The internal cast used by Whitfield as the original for his figures 1 and 2 of C. multi- radiatum seems to be a member of this species also; a specimen in the recent collections of the Survey from the Navesink marl near Crawfords Corner agrees almost exactly with this illustration, and it is undoubtedly a member of the species under discussion. The enlarged illustration, figure 3, given to represent the surface characters of this same species, is much overdrawn, the original mould from which the gutta-percha impres- sion was taken being altogether too imperfect to show to what species it belongs."— Weller, 1907.
The casts of C. tenuistriatum Whitfield are readily separable from those of C. dumosum Conrad by the much higher relative altitude and the trun- cated posterior margin. The resemblance to the casts of C. kiimmeU Weller is much closer, but the umbones are somewhat less elevated and less acute and the anterior adductor muscle scar much less prominent.
Occurrence. — MATAWAN FORMATION. Park Point, and ? Ulmstead Point, Anne Arundel County. MONMOUTH FORMATION. ? Jones farm, Burklow's Creek, Cecil County.
Collections. — Maryland Geological Survey, Columbia Univerisity, Xew Jersey Geological Survey.
MARYLAND GEOLOGICAL SURVEY 673
Outside Distribution. — Matawan Formation.. Merchantville clay marl, Marshalltown clay marl, Wenonah sand, New Jersey. Monmouth Forma- tion. Navesink marl, New Jersey.
CARDIUM KUMMELI Weller
Cardium kummeli Weller, 1907, Geol. Survey of New Jersey, Pal., vol. iv, p. 585, pi. Ixvi, figs. 1-3.
Description. — " The dimensions of a rather small internal cast of a right valve are : Height 45 mm., width 34 mm., convexity 17.5 mm. Large individuals sometimes attain a height of 70 mm. or more. Shell subovate in lateral view, cordate in end view. Beaks of the internal casts greatly elevated above the hinge line, pointed and incurved. Hinge line arcuate; anterior margin regularly rounded from the extremity of the hinge line to the middle of the basal margin ; postero-basal margin a little more sharply rounded; posterior margin convex, a little straighter than the anterior. Valves strongly convex or gibbous, most prominent, but not at all angular, along an oblique line from the beaks to the postero- basal extremity, the posterior slope more abrupt than the anterior. Mus- cular impressions large, the anterior ones deeply impressed above, the pos- terior one scarcely differentiated from the general surface of the casts. Hinge characters not seen. Inner free margins of the valves apparently not crenate. Shell substance thick, rugose externally. The surface mark- ings consist of strongly elevated, rounded, radiating costae, narrower than the interspaces; on a specimen about 55 mm. in length the distance between these ribs from center to center at the middle portion of the shell margin is about 2 mm. or a little less. Each third interspace is occupied by a row of strong and thick spines rising 1 or 2 mm. above the tops of the costee when complete, subcircular in cross-section, their bases occupying the entire width of the furrow, the space between successive spines being about equal to the thickness of the spines themselves ; in some cases the bases of the spines are thickened longitudinally so that they occupy essen- tially the entire furrow, in which case the two bounding costse with the row of spines rising from the intervening furrow appear to form alto- gether one broad rib supporting a row of strong spines. The two furrows
674 SYSTEMATIC PALEONTOLOGY
intervening between the rows of strong spines are each occupied by a row of very much smaller, laterally compressed spines whose bases are more or less connected.
" There is considerable variation shown in the surface markings of different individuals of this species, and the extremes might be taken as the representatives of distinct species or even of distinct subgenera. In its typical form, as seen in the Tinton beds, the species exhibits clearly the characteristics of the subgenus Criocardium, the rows of spines rising from the interspaces betwen the radiating costa3 of the shell. In some specimens the bases of the larger spines or nodes are confluent and appear to entirely fill the interspace occupied by them, so that the two bounding costae with the row of spines together seem to constitute a single broad rib crowned with a row of strong nodes. At the same time the rows of secon- dary nodes are sometimes confluent at their bases and form a continuous secondary rib, perhaps nodose on top, and about equaling in height and size the primary costas, so that there seem to be three costae of nearly equal size in the broad interspace between the rows of large nodes and their included bounding costae. In the extreme development of the rows of secondary nodes their bases are confluent and they increase in size and height so as to occupy the whole of the interspaces, obliterating entirely the primary costae, so that the surface of the shell is apparently marked by radiating rows of tubercles which apparently do not rise from interspaces between costae, but directly from the surface, each third row being much larger and stronger than the two intervening ones.
" It is possible that larger collections of more perfectly preserved material than is now available would show that more than one species has been included under this head, but so far as can be determined from present collections, all these forms seem to run together. The typical form of the species, however, is that in which the nodes rise distinctly from the interspaces, showing the characters clearly of the subgenus Crio- cardium, and which has been recognized only in the Tinton beds.
" In its somewhat elongate and slender form, the species in the form of internal casts somewhat resembles the casts of C. spillmani and they have sometimes been so identified. It does not grow so large as that
MARYLAND GEOLOGICAL SURVEY 675
species, however, it lacks the radiating ribs usually impressed upon the posterior slope of C. perelongatum, and the anterior muscular scar is not so low in position.
" In the collections of the National Museum at Washington this species is represented by numerous examples from the South, which have usually been referred to C. dumosum. These southern specimens are perfectly pre- served shells which are smaller than the usual examples from the Tinton beds in New Jersey, but their surface markings are identical with those of the type specimen. The species differs from C. dumosum in its more elongate form and in the much coarser surface markings. C. tippana is another allied form in which the surface markings are fully as coarse as in C. kiimmeli, but there is only a single row of smaller tubercles between the larger ones in that species, instead of two as in C. kummeli." — Weller, 1907.
Type Locality. — Beers Hill Cut, New Jersey.
The casts of C. Tcummeli are characterized by higher, more acute umbones than those of either C. dumosum or C. tenuistriatum. It is further differentiated from C. dumosum by the relatively higher altitude, the less equilateral outline and the more prominent anterior adductor muscle scar.
Occurrence. — MATA WAIST FORMATION. Camp Fox, Post 236, Post 218, Camp U & I, Post 196, one-eighth of a mile west of Summit Bridge, Chesapeake and Delaware Canal, Delaware; 1 mile west of Chesterfield, Anne Arundel County, Maryland. MONMOUTH FORMATION. Two miles west of Delaware City, on John Higgins farm, DelaAvare; Brooks estate near Seat Pleasant, 1 mile west of Friendly, Prince George's County, Maryland.
Collections. — Maryland Geological Survey, New Jersey Geological Sur- vey, U. S. National Museum.
Outside Distribution. — Monmouth Formation. Navesink marl, Tinton beds, New Jersey. Ripley Formation. Exogyra costata zone, Eufaula, Alabama; Quitman, Union and Tippah counties, Mississippi. Extreme top of zone, Pataula Creek, Georgia; Barbour and Henry counties, Ala- bama.
676 SYSTEMATIC PALEOXTOLOGY
Superfamily VENERACEA
Family VENERIDAE
Genus DOSINIA Scopoli
[Introd. ad Hist. Nat. 1777, p. 399]
Type. — Dosinia africana Hanley.
" Animal with a large arcuate foot and closely united siphons. Com- plete dental formula (the posterior right cardinal, being extremely thin,
is often broken off, eroded, or obsolete) L' 0101010.010 The thick
E. 1010101.101
middle cardinals are often bifid or excavated. Valves suborbicular, gen- erally compressed, with a long and strong ligament seated in a groove and enfolding a heavy resilium, lunule small, impressed ; escutcheon narrow, nearly linear or absent; hinge plate broad and thick, valve margins smooth ; pallial sinus rather long and usually acute, anterior lateral teeth nearly obsolete and usually simple; sculpture usually of elegantly con- centric grooves and interspaces, sometimes raised into lamella at the borders of the lunule and escutcheon, crossed rarely with weak radial threads; coloration of the recent species rarely disposed in patterns and usually pale, many species being white. The periostracum is usually thin and polished."— Ball, 1903.1
The genus was initiated in the Cretaceous but not very well represented. The rather large and rotund shells are, however, very much in evidence in the Tertiary and Eecent faunas. The Becent species number about one hundred, and have an almost universal distribution in the temperate and warmer waters.
DOSINIA OBLIQUATA Conrad
Dosinia obliguata Conrad, 1860, Jour. Acad. Nat. Sci., Phila., 2d ser., vol. iv,
p. 278, pi. xlvi, fig. 2. Dosinia oUiquata Meek, 1864, Check List Inv. Fossils N. A., Cret. and Jur.,
p. 13.
Description. — " Lentiform, very oblique ; beaks almost terminal ; minute, concentric, regular, closely arranged, impressed lines on the anterior side." — Conrad, 1860.
Etymology: Dosin, a Sengalese name used by Adanson as a specific name. 1 Trans. Wagner Free Inst. Sci., Phila., vol. iii, pt. vi, p. 1227.
MARYLAND GEOLOGICAL SURVEY 677
Type Locality. — Owl Creek, Tippah County, Mississippi.
Conrad's figure somewhat belies his description. The shell is rather small and thin, subcircular and feebly convex; the umbones are rather gibbous for the genus, the apices acute and prosogyrate, rising above the dorsal margin and approximately central, not terminal in position. The area of maximum inflation extends obliquely backward from the umbones to the posterior ventral margin widening toward the base, thus giving to the shell the characteristically oblique aspect which inspired the name. The anterior end is broadly and symmetrically rounded, the posterior obscurely truncated, the base line arcuate. The external surface is sculp- tured with very fine, overlapping concentric laminae, most sharp and most regular in th eumbonal region and along the anterior margin. The char- acters of the interior are not known.
The species is represented in Maryland by a single imperfect valve.
Occurrence. — MONMOUTH FORMATION. Brooks estate near Seat Pleas- ant, Prince George's County.
Collection. — Maryland Geological Survey.
Outside Distribution. — Ripley Formation. Exogyra costata zone, Tippah County, Mississippi.
Genus CYCLINA Deshayes [Traite Elem., vol. i, 1849, p. 623]
Type. — Venus sinensis Gmelin = Venus chinensis Gmelin.
" The dental formula is L- 010101Q. The fourth, or posterior, right
E. 1010101
cardinal is nearly obsolete; the one in front of it and the anterior left cardinal are bifid. The shell is suborbicular, nearly equilateral, and plump; the ligament uncovered but deep-set; there is neither a defined lunule nor escutcheon, the sculpture is faint and chiefly concentric, feebly reticulated by radial stria ; the hinge plate is broad, the inner margins of the valves crenulate, the pallial sinus moderate in size, acutely angular in front, and obliquely ascending. There is no trace of lateral teeth; the periostracum is polished and translucent, the coloration tinted, without
Etymology: /a'/cXcs, circle.
678 SYSTEMATIC PALEONTOLOGY
a distinct pattern. The typical forms are denizens of China, Japan, and Korea. The two American forms which have been referred to this genus by Deshayes are discussed under the head of Cyclinella, and are probably allied to Mysia. They differ conchologically by having smooth inner margins to the valves, a defined lunule, no trace of the fourth right car- dinal tooth, and purely concentric sculpture." — Ball, 1903.1
CYCLINA PARVA n. sp. Plate XLI, Figs. 5, G
Description. — Shell porcellanous, rather heavy for its small size, sub- circular in outline, moderately inflated, the maximum convexity above the median horizontal; umbones subcentral, rather prominent, with fine prosogyrate apices placed a little in front of the median vertical ; lunule and escutcheon not differentiated ; dorsal margins obliquely truncate, the anterior shorter and more gently sloping than the posterior; anterior extremity broader and smoothly rounded; posterior extremity obscurely truncate ; base line evenly arcuate ; external surface smooth, excepting for faint concentric striations and two or three well defined resting stages, the striae least feeble toward the lateral and ventral margins, but absent alto- gether in the immediate vicinity of the umbones; ligament external, opis- thodetic, mounted on a rather short and slender nymph ; cardinals three in number in each valve, radiating fan-like from beneath tin- umbones, the anterior cardinal in the right valve thin, laminar and somewhat pro- duced, the middle cardinal stouter, widening ventrally, the posterior obliquely produced and asymmetrically bifid; anterior and medial car- dinal of the left valve united beneath the umbones, the anterior slender, laminar, elongated, the medial shorter, slightly elongated and stouter, the posterior very slender and not very much produced ; adductor scars rela- tively large, narrow but elongated, placed well up near the extremities of the hinge line; pallial sinus distinct, acutely angulated at about 90°, the breadth and depth approximately equal; pallial line distant; inner ven- tral margins simple.
1 Trans. Wagner Free Inst. Sci., Phila., vol. iii, pt. vi, p. 1234.
MARYLAND GEOLOGICAL SURVEY 679
Dimensions. — Altitude 3.7 mm., latitude 4 mm., semi-diameter 1.4 mm.
Type Locality. — Brooks estate near Seat Pleasant, Prince George's County.
This small Yenerid is quite unique in the molluscan faunas of the East Coast Upper Cretaceous.
Occurrence. — MONMOUTH FORMATION. Brightseat, Brooks estate near Seat Pleasant, Friendly, McNeys Corners, Prince George's County.
Collection. — Maryland Geological Survey.
Genus MERETRIX Lamarck [Prodrome Nouv. Class. Coq., 1799, p. 85]
Type. — Venus Meretrix Linne.
" Shell trigonal, plump, subequilateral, thin, smooth, with a vernicose periostracum and a peculiar olivaceous tone of coloration; lunule and escutcheon not distinctly defined ; cardinals three in each valve, with well- marked anterior laterals; the middle left and two anterior right cardinals entire, smooth, the others grooved or bifid; right nymph and posterior left cardinal corrugated ; dorsal margins, beyond the hinge plate, grooved to receive the edge of the opposite valve; internal margins smooth, the pallial line with a shallow arcuate flexuosity but no angular sinus." — Ball, 1903.1
The genus was initiated in the Cretaceous. The recent species are most abundant in the Pacific.
MERETRIX CRETACEA (Conrad) Weller
Mora cretacea Conrad, 1870, Am. Jour. Conch., vol. vi, p. 72, pi. iii, fig. 8. Mora cretacea Whitfield, 1885, Mon. U. S. Geol. Survey, vol. ix, p. 167, pi.
xxiii, figs. 16, 17.
Mora cretacea Johnson, 1905, Proc. Acad. Nat. Sci., Phila., p. 16. Meretrix cretacea Weller, 1907, Geol. Survey of New Jersey, Pal., vol. iv,
p. 608, pi. Ixvili, figs. 4-7.
Etymology: The specific name of the type.
1 Trans. Wagner Free Inst. Sci., Phila., vol. iii, pt. vi, p. 1259.
680 SYSTEMATIC PALEONTOLOGY
Description. — " Subtriangular, subequilateral, convex; end margins acutely rounded; umbo slightly prominent; lunule lanceolate, slightly defined by an impressed line; ventral margin rounded." — Conrad, 1870.
Type Locality. — Haddonfield, New Jersey.
" Shell below medium size, the dimensions of an average example are : Height 16.5 mm., approximate length 23 mm., convexity of one valve 5 mm.; somewhat triangularly subelliptical in outline. Valves moder- ately convex, beaks small, situated anterior to the middle ; antero-cardinal margin concave ; anterior margin rather sharply rounded above, curving more- gently below and passing without interruption into the broadly rounded ventral margin; posterior margin rather short, obscurely sub- truncate; post-cardinal margin long, gently convex, meeting the antero- cardinal margin at the beak in an angle of 120°. Postero-cardinal mar- gin somewhat inflected, especially towards the beak; antero-cardinal margin inflected in front of the beak to form a shallow lunule of moderate width. Surface of shell marked by more or less irregular, concentric lines of growth only. Hinge of the left valve with three cardinal teeth diverging from beneath the beak, the two anterior ones of about equal length, extending directly beneath the beak with a triangular pit between them, the posterior one much more oblique and more elongate. In front of the cardinal teeth is a single low lateral beneath the lunule and parallel with the shell margin. In the right valve there are two divergent, bifid cardinal teeth with a pit beneath the lunule for the reception of the ante- rior lateral tooth of the oposite valve." — Weller, 1907.
The only evidence of the former presence of this species in Maryland and Delaware is a single imperfect cast from the Chesapeake and Dela- ware Canal.
Occurrence. — MATAWAN FOKMATIOX. Summit Bridge, Chesapeake and Delaware Canal, Delaware.
Collections. — Maryland Geological Survey, Philadelphia Academy of Natural Sciences, New Jersey Geological Survey.
Outside Distribution. — Matawan Formation. Woodbury clay, Mar- shalltown clay marl, New Jersey.
MARYLAND GEOLOGICAL SURVEY 681
Genus ANTIGONA Schumacher1 [Essai, 1817, pp. 51, 154]
Type. — Antigona lamellaria Schumacher.
" Shell smaller and more trigonal, less rotund than Cytherea s. s. ; the left anterior lateral lamellifonn and larger, with a perceptible socket in the right valve ; the posterior right cardinal broad and deeply bifid ; pal- lia! sinus small, triangular." — Ball, 1903.2
Subgenus APHRODINA Conrad [Am. Jour. Conch., vol. iv, 1869, p. 246]
Type. — Meretrix tippana Conrad.
" Shell rounded or suboval, striated or sulcated ; hinge in the left valve with three diverging cardinal teeth, the anterior tooth as thick as the middle one or thicker, and a straight, compressed, transversely rugose lateral tooth parallel with the margin of the shell above it; pallial sinus deep, and similar to that in Caryatis Boemer." — Conrad. 1868.
" Shell concentrically striated, with a circumscribed lunule, but no defined escutcheon; inner margins smooth; pallial sinus ample, free, ascending, rather rounded in front; hinge with three cardinals in each valve, the right posterior cardinal bifid ; an elongate anterior lateral cor- rugated on both sides and received into a corrugated pit in the right valve ; nymphs plain." — Ball, 1903.3
ANTIGONA (APHRODINA) TIPPANA Conrad Plate XL, Figs. 3, 4
Meretrix tippana Conrad, 1858, Jour. Acad. Nat. Sci., Phila., 2d ser., vol.
iii, p. 326, pi. xxxiv, fig. 18. Dione tippana Meek, 1864, Check List Inv. Fossils, N. A., Cret. and Jur.,
p. 13..
Etymology: Antigone, daughter to CEdipus.
1 Cytherea Bolten, 1798, (part) Mus. Boltenianum, ed. i, p. 177; 1819, ed. ii, p. 124. Venus puerpera Linnaeus. Not Cytherea Fabricius (Diptera), 1795, Lamarck, 1806, nor H. and A. Adams, 1856.
Callista Fischer, 1887, Man. de Conch., p. 1084. Venus verrucosa Linn6. Not Callista Morch, 1853.
2 Trans. Wagner Free Inst. Sci., Phila., vol. iii, pt. vi, p. 1273.
3 Trans. Wagner Free Inst. Sci., Phila., vol. iii, pt. vi, p. 1272.
682 SYSTEMATIC PALEOXTOLOGY
Aphrodina tippana Conrad, 1868, Cook's Geol. of New Jersey, p. 727. Aphrodina tippana Conrad, 1869, Am. Jour. Conch., vol. iv, p. 246, pi. xviii,
fig. 5. Aphrodina tippana Whitfield, 1885, Mon. U. S. Geol. Survey, vol. ix, p. 154,
pi. xxii, figs. 6, 7.
Aphrodina tippana Johnson, 1905, Proc. Acad. Nat. Sci., Phila., p. 16. Meretrix tippana Weller, 1907, Geol. Survey of New Jersey, Pal., vol. iv, p.
607, pi. Ixviii, figs. 1, 2 (ex parte).
Description. — " Subtriangular, obsoletely striated concentrically ; ante- rior sides slightly compressed, with an ascending basal margin, extremity rather acutely rounded, distant from the apex ; base a little prominent in the middle, subtruncated on either side; posterior end but slightly more obtuse than the anterior; beaks prominent." — Conrad, 1858.
Type Locality. — Owl Creek, Tippah County, Mississippi.
Shell rather large and heavy, ovate-trigonal in outline, evenly but strongly inflated ; lunule narrow, elongated, denned by an impressed line ; area behind the umbones somewhat flattened but escutcheon not differenti- ated ; umbones rather prominent by reason of their position at the apex of an angle of a little more than 90° ; umbones evenly rounded but not strongly inflated, the apices incurved, prosogyrate, slightly anterior in position ; anterior extremity strongly arcuate, even a little nasute in front of the lunule ; posterior dorsal margin obliquely arcuate, the lateral mar- gin obscurely truncate ; ventral margin convex, more strongly upcurved in front than behind ; external surface concentrically striated with a vigorous incremental sculpture which becomes increasingly prominent toward the ventral margin; ligament external, opisthodetic, mounted 011 rather a slender nymph which extends a little less than half-way down the dorsal margin ; cardinals three in number in each valve, the anterior cardinal of the right valve short and slender, the middle cardinal trigonal, the poste- rior laminar and elongated, anterior cardinal of the left valve trigonal and stouter than that of the right, the middle cardinal rather short and slender, the posterior elongated parallel to the nymph, a single short lateral elon- gated parallel to the lunular margin in the right valve, received in a double socket in the left; muscle impressions distinct but not conspicuous, the anterior semi-elliptical, the posterior subcircular ; pallia! line distinct, the
MARYLAND GEOLOGICAL SURVEY 683
sinus linguiform and obliquely ascending almost but not quite to the median horizontal.
Aphrodina tippana Conrad is one of the most widely distributed and most characteristic species of the Exogyra costata zone. Weller has deter- mined some casts from the Matawan of New Jersey by this name, but they seem to show at least a subspecific difference in the shorter, relatively higher outline and the less produced, more broadly rounded posterior end.
Occurrence. — MONMOUTH FORMATION. Brightseat, Prince George's County.
Collections. — Maryland Geological Survey, Philadelphia Academy of Natural Sciences, U. S. National Museum.
Outside Distribution. — Magothy Formation. New Jersey. Ripley Formation. Exogyra costata zone, Union, Tippah and Alcorn counties, Mississippi; Georgia; Eufaula, Alabama. Extreme top of zone, Chatta- hoochee River, Georgia.
Genus LEGUMEN Conrad [Jour. Acad. Nat. Sci., Phila., 2d ser., vol. iii, 1858, p. 325]
Type. — Lcgumen ellipticus Conrad = L. planulatum Conrad.
" Shell equivalve, very inequilateral, flattened ; hinge with two very slender teeth in the right valve under the beak, and one posterior, very oblique, prominent, lamelliform tooth." — Conrad, 1858.
Legumen like the associated Leptosolen occurs most frequently in the form of casts, but it is readily differentiated from the latter by the rela- tively greater altitude, the ellipsoidal rather than cylindrical outline, and particularly by the absence of a sulcus across the umbones.
The genus, though quite abundant locally, has a restricted distribution within the Cretaceous.
A. Altitude of shell not more than half the latitude Legumen planulatum
B. Altitude of shell equal to or greater than half the latitude
Legumen carolinense
Etymology: Legumen, a bean. 45
684 SYSTEMATIC PALEONTOLOGY
LEGUMEN PLANULATUM Conrad Plate XL, Figs, 5-7
Solemya planulata Conrad, 1853, Jour. Acad. Nat. Sci., Phila., 2d ser., vol.
ii, p. 274, pi. xxiv, fig. 11.
Legumen ellipticus Conrad, 1858, Ibidem, vol. iii, p. 325, pi. xxxiv, fig. 19. Legumen appressus Conrad, 1858, Ibidem, p. 325. Legumen appressa Meek, 1864, Check List Inv. Fossils, N. A., Cret. and
Jur., p. 15.
Legumen elliptica Meek, 1864, Ibidem. Legumen planata Meek, 1864, Ibidem.
Legumen ellipticus Conrad, 1868, Cook's Geol. of New Jersey, p. 727. Legumen appressus Conrad, 1868, Ibidem.
Legumen planulatus Gabb, 1876, Proc. Acad. Nat. Sci., Phila., p. 304. Legumen planulatum Whitfield, 1885, Mon. U. S. Geol. Survey, vol. ix, p.
184, pi. xxv, figs. 3, 4.
Legumen appressum Whitfield, 1885, Ibidem, p. 185, pi. xxv, figs. 6-8. Legumen ellipticum Whitfield, 1885, Ibidem, p. 184, pi. xxv, fig. 5. Legumen planulatum Johnson, 1905, Proc. Acad. Nat. Sci., Phila., p. 17. Legumen appressum Johnson, 1905, Ibidem. Legumen ellipticum Johnson, 1905, Ibidem. Legumen planulatum Weller, 1907, Geol. Survey of New Jersey, Pal., vol.
iv, p. 612, pi. Ixix, figs. 3-7.
Description. — " Elliptical, compressed, sides flattened ; end margins rounded; hinge and basal margins nearly parallel." — Conrad, 1853.
Type Locality. — Monmouth County, New Jersey.
Shell very thin and porcellanous, much compressed, transversely ellip- soidal in outline, slightly expanding posteriorly; dorsal and ventral mar- gins subparallel; posterior extremity strongly arcuate, anterior end of shell slightly constricted directly in front of the umbones; the lateral margin evenly and strongly convex; lunule and escutcheon not defined; umbones very low and compressed with sharp and prosogyrate apices placed within the anterior third; external surface adorned with a sharp incremental sculpture, almost obsolete in the umbonal region and along the extreme dorsal margin, sharpest and most regular near the anterior ventral margin; radial sculpture not developed; ligament submarginal, seated on a nymph not quite half as long as the posterior dorsal margin ; cardinals three in number in each valve ; the anterior and middle cardinals of the right valve thin, laminar and rather short, diverging beneath the
MARYLAND GEOLOGICAL SURVEY 685
umbones at rather a small angle; the posterior cardinal also thin and laminar, finely bifid, much elongated and set close under the nymph to which it is approximately parallel ; anterior cardinal of left valve thin and laminar, but quite prominent, fitting between the anterior and middle cardinals of the right valve ; the middle and posterior cardinals of the left valve laminar and elongated, the posterior more produced and narrowly sulcate, both of them placed far back under the dorsal margin and diverg- ing from one another and from the ligament nymph at a very small angle in order that they may receive the posterior cardinal of the right valve ; muscle impressions small, obscure; pallia! line running close to the ventral margin; sinus short, broad, acutely angulated at its anterior extremity.
Occurrence. — MATAWAX FORMATION. Three-quarters of a mile south- west of Ulmstead Point, Anne Arundel County. MOXMOUTH FORMATION. Freeman's Creek, Kent County ; Brightseat, Brooks estate near Seat Pleas- ant, Friendly, McNeys Corners, 2 miles south of Oxon Hill, Prince George's County.
Collections. — Maryland Geological Survey, Philadelphia Academy of Xatural Sciences, New Jersey Geological Survey, U. S. National Museum.
Outside Distribution. — Matawan Formation. Merchantville clay marl, Woodbury clay, Wenonah sand, New Jersey. Monmouth Formation. Xavesink marl, Red Bank sand, New Jersey. Black Creek Formation. North and South Carolina. Eutaw Formation (Tombigbee sand mem- ber). Exogyra ponderosa zone, Mortoniceras subzone, Georgia. Ripley Formation. Exogyra ponderosa zone, Barbour County, Alabama. Exo- gyra costata zone, Schley County, Georgia ; Euf aula, Alabama ; Union and Tippah counties, Mississippi. Extreme top of zone, Pataula Creek, Georgia. Selma Formation. Exogyra costata zone, Wilcox County, Ala- bama ; east-central Mississippi.
LEGUMEN CAROLINENSE (Conrad)
Baroda carolinensis Conrad, 1875, Kerr's Rept. Geol. Survey, North Caro- lina, Appendix, pp. 8, 9, pi. ii, fig. 10.
Description. — " Shell oblong, very inequilateral, convex, with a few slightly impressed concentric furrows; posterior cardinal margin long,
686 SYSTEMATIC PALEONTOLOGY
straight, oblique ; margins rounded ; umbonal slope undefined and regu- larly convex with post-umbonal slope. This is the first species found in America, and represents an interesting exclusively Cretaceous genus. The hinge fortunately can be obtained in perfection at Snow Hill. The genus is common to the Senoniah strata in America, Europe and Southern India."— Conrad, 1875.
Type Locality. — Snow Hill, North Carolina.
Ligament external, opisthodetic, nymphs elongated and produced more than half the length of the dorsal margin ; cardinals three in number in right valve, two in left; the anterior and middle cardinals of the right valve rather short, simple and not very heavy, diverging at rather a small angle from beneath the umbones, the posterior cardinal laminar obliquely elongated and placed far back toward the nymph; cardinals of the left