No. 109.' 



121 



This species bears some resemblance to P. knighti of Sowerbt, and 

 may be regarded as tbe nearest representative of that shell in our rocks : 

 it differs, however, in its smaller size, and in having stronger and much 

 less regular plications. 



The young individuals of this species bear a close resemblance, in gene- 

 ral form and character, to Rhynchonella (Atrypa), and two varieties have 

 been thus described by Mr. Conrad as distinct species. There are still 

 some intermediate gradations wanting, to show the relations of figs. 4 and 

 6 with 9 and 10, of which I have fragments. A specimen more recently 

 obtained, of the dimensions of fig. 6, shows the internal structure of Pen- 

 laments in the most perfect manner. 



Geological posit?o7i and locality. Schoharie grit, Albany and Schoharie 

 counties ; and Onondaga limestone of the Upper Helderberg group, Erie 

 county, etc. 



Peniamerus arattjs. 



