111896 
The Nautilus. 
Vol. viii. MARCH, 1895. : No. 11 
UNIO OCHRACEUS AND CARIOSUS. 
BY CHARLES TURKEY SIMPSON. 
The senior editor of the Nautilus has asked me to point out in 
a clear concise way the specific differences between Unio ochraceua 
Say, andj Unio cariosus Say. They were both described in Nichol¬ 
son’s Encyclopedia, in an article on conchology, by Say ; and the 
work, which is now long out of print, is exceedingly rare, and out 
of the reach of the ordinary student. 
Union ochraceus Say. 
Both belong to a great assembly of North American forms fairly 
typified by the well known Unio occidens, it being one of the few 
groups that are well represented both in the Mississippi Valley and 
