NATURAL SCIENCES OF PHILADELPHIA. 
15 
Resembles in external form Areapinguis, de Kon., (Anim. Foss., 116, ii. 11). 
Compare also Cypricardia parvula, {pi. ii. fig. 3). 
The Hamilton group of New York furnishes a fossil similar to the above ; 
and the Waverly sandstone of Ohio another similar, perhaps identical, one. 
* 
Sanguinolites (?) jejunus, n. sp.—Shell of moderate size, equivalve, trans¬ 
verse; beaks small, barely elevated above the hinge, slightly inflected, one- 
third the shell-length from the anterior end; height fully half the length; 
hinge-line extended ; dorsal slope erect, marked by an internal ridge ; margin 
slightly inflected, if at all, though some indication exists of a very narrow 
escutcheon; anterior lunette equally inconspicuous; ventral margin symmetri¬ 
cally arcuate between the extremities, with which it connects by similar gradu¬ 
ally increasing curvatures; posterior end truncate for a short space near the 
termination of the hinge-line, with which it forms an angle of about 130®; 
anterior end semi-elliptically rounded. Valves somewhat appressed; greatest 
distension one-fourth the distance from the beak to the venter. Surface of 
cast marked by faint lines of growth. 
Length -86 (100); height -48 (55); length of anterior end *31 (36); of pos¬ 
terior -55 (64) ; thickness of both valves -20 (23). 
Some specimens associated here are relatively shorter posteriorly, but not 
otherwise distinguishable. 
McCoy’s generic names and distinctions,— Sanguinolites and Leptodomus ,— 
seem preferable to King’s AUorisma , inasmuch as the latter name, besides being 
subsequent in time, was originally defined under an erroneous idea, and was 
finally left to embrace shells regarded as sinupallial,—a character which does 
not seem to belong to the so-called Allorismas of the Palaeozoic period. San¬ 
guinolites lowensis, and probably some of the others just described, are allied in 
form to Cypricardia; but I agree with Pictet and others in believing that, 
while we have no evidence of the existence of the teeth of Cypricardia in any 
of the Palaeozoic species generally referred to that genus, it is more natural to 
throw them into another association. Moreover, the sharply-inflected dorsal 
margin and broad, elongate posterior escutcheon, present in all the species of 
Coelonotidse, would seem to indicate real affinities, and thus withdraw the 
AUorisma type entirely from the association in which it has been placed. 
Cypricardia ? rigida , White and Whitfield, from the same rocks, is & Sanguinolites. 
CARDIOMORPHA, de Koninck. 
Cardiomorpha trigonalis, n. sp.—Shell smaller of moderate size, triangular, 
rather ventricose, with elevated, incurved beaks. Ventral margin slightly con¬ 
vex anteriorly, slightly sinuate near the posterior angle ; anterior angle regu¬ 
larly rounded to the subtruncate anterior side; posterior angle rather acute, 
formed by the termination of the sharp postumbonal ridge, from which the 
surface descends precipitously to the truncate posterior margin. Hinge-line 
short, rounded, edentulous. Greatest thickness a little above the middle of the 
shell. Surface marked only by faint incremental striae; younger specimens 
smooth. 
Length *82 (100) ; height *72 (88) ; thickness of both valves *50 (61). 
This species has been sometimes regarded as C. rhomboidea 1 Hall, but none 
of the numerous specimens of it exhibit the least trace of radiating lines. 
The outline, moreover, is subtriangular instead of subrhomboidal. (Compare 
with C? triangulata , Swallow, St. Louis Trans., i. 655.) 
ARCA, Linnaeus. 
Arca modesta, n. sp.—Shell small, very ventricose, quadrate-oval, with a 
posterior alate prolongation of the hinge-line. Beaks subterminal, incurved, 
separated by a ligamental area; posterior hinge-line straight, nearly as long 
as the shell. Umbonal ridge and body of the shell inflated to the ventral mar- 
1863.] 
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