No. 109."! 



121 



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

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

 it dififers, 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 Rhynchoyiclla [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- 

 tameriis in the most perfect manner. 



Geological position and locality. Schoharie grit, Albany and Schoharie 

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

 county, etc. 



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Pentameeus ARAXrS. 



