Elymella levata. 
tion. See page 504. 
A specimen retaining both valves in conjunc- 
Hamilton Group. Schoharie County, N. Y. 
Panenka alternata. View of a large right, valve showing the form of the shell and the general charac¬ 
ter of the surface ornamentation. The central portion of the valve has been broken away, and the radii are 
obscure on the marginal portions. The specimen is preserved in the dolomitic limestone of the Upper 
Helderberg group, from near Columbus, Ohio. See page 416. 
