«8a PALa:0NT0LOGT OP 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 strise; while in another specimen of the right 

 valve, having the surface much worn, the radiating stria? 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 lamella*. 



Fig. 1, The right valve, having the shell nearly csfoliatod. 



Fig. 2. The left valve of the same species, preserving some small pieces of the shell. 



Geological fosition and locality. In the shaly limestone of the Lower Heldcrberg 

 group : Helderberg mountains, Albany and Schoharie counties. 



Avicula spiiiulifera ( n. s.). 



Plate LI. Fia. 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. 



ScBFACE marked by numerous strong radiating striaD which are unequally 

 dichotomized, and crossed by regular elevated subimbricating lamellose 

 etrioB, 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, 



