101 



[ Senate 



Pentamerus verneuili. 



Pal. N.Y. Yol.iii, pi. 48, f. 1. 



Shell suhglobose ; transverse diameter generally greater than the 

 height : ventral valve more depressed than the opposite, having 

 a distinct sinus, commencing near the beak and regularly wi- 

 deniiu' and deepening to the front, where it terminates in a short 

 truncated extension fitting into a corresponding depression in 

 the front of the other valve ; beak shorter than the opposite, 

 perforated ])y a trianguhir foramen, which is generally covered 

 by the strongly gibbous incurved beak of the other valve : 

 dorsal valve very much elevated ; beak extremely gibbous and 

 incurved. Surface marked by from twenty-four to thirty sharply 

 angular ek^vated plications, which increase by interstitial addi- 

 tion and iMfurcation : from four to six of the plications on the 

 ventral valve usually occupy the sinus ; while from five to eight 

 of those on the dorsal valve are very slightly elevated, so as to 

 form a flat rather indistinct mesial fold. 



This beautiful species is unlike any form known to me in our rocks : it 

 bears an analogy to AtrTjpa iiilcrplicata of the Niagara group, which is 

 probably a Penlamerus, though its internal characters have not yet been 

 seen. This species will, however, be easily distinguished from that, by its 

 larger size and more globose form, as well as more numerous and sharper 

 plications. 



Geological 'position and locality. Shaly limestone of the Lower Helder- 

 berg group, Albany and Schoharie counties. 



X 



Pentamerus verneuili. 



