PAL/EONTOLOGY OF NEW-YORK. 
The specimens which have been seen are of the right and left valves of different 
individuals; the right valve being nearly flat, and the opposite one very slightly 
convex. The shell is almost entirely removed from two of these specimens, and the 
cast of one shows some faint radiating striae; while in another specimen of the right 
valve, having the surface much worn, the radiating striae are preserved on the cen¬ 
tral portions of the shell, but do not seem to have extended to the sides, which are 
marked only by the concentric lamellae. 
Fig. 1. The right valve, having the shell nearly exfoliated. 
Fig. 2. The left valve of the same species, preserving some small pieces of the shell. 
Geological position and locality. In the shaly limestone of the Lower Helderberg 
group : Helderberg mountains, Albany and Schoharie counties. 
Avi C5ila splnulifera (n. s.). 
Plate LI. Fig. 3 & 4. 
Shell obliquely and broadly subovate, inequilateral : posterior side pro¬ 
duced and regularly rounded; anterior side shorter and regularly 
curved, the basal margin forming part of an elliptic curve ; hinge-line 
nearly equal to the greatest width of the shell : left valve moderately 
convex, the greatest convexity being near the middle or towards the 
umbo; right valve nearly flat, or very slightly convex : anterior wing 
triangular, extending as far as the anterior margin of the shell, or¬ 
namented on its upper margin with a few short spines; posterior wing 
broader, and extending scarcely as far as the posterior margin of the 
shell. 
Surface marked by numerous strong radiating striae which are unequally 
dichotomized, and crossed by regular elevated subimbricating lamellose 
striae, giving the entire surface a cancellated appearance. The radiating 
striae do not appear on the wings of the left valve, but upon these parts 
the concentric striae are closely crowded : on the right valve, some 
faint indications of radiating striae appear upon both the wings. 
The only specimens seen are the interior of a right valve from which most of the 
posterior wing is broken, and the impression made by the exterior of the left valve, 
