101 



[ Senate 



Pentamerus verneuili. 



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



Shell snbglobose ; transverse diameter generally greater than the 

 lieight : ventral valve more depressed than the opposite, having 

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

 dening 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 by a triangular 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 elevated plications, which increase by interstitial addi- 

 tion and bifurcation : 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 Atrypa inierflicaia of the Niagara group, which is 

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

 seen. This species will, howev^er, 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. 



Pentamerus verneuili. 



