No. 109.] 



83 



pressed upon the casts, will prevent it from being confounded with any 

 other species found in our rocks. 



In many respects it resembles R. spedosa, which may be regarded aa a 

 representative form in the Maryland rocks : it is, however, distinguished 

 from that shell by its larger size, its more elevated dorsal valve and re- 

 latively broader form, and its broad shallow rounded sinus near the front 

 of the ventral valve. 



Geological position and locality. Oriskany sandstone, Albany and Scho- 

 harie counties. 



Rhynchoneilv. baseandi. 



