figure is from a specimen from the Scioto, given me 

 by my friend, Dr. William Blanding. 



UNIO OVATUS. 



Plate II. 

 DESCRIPTION. 



Shell subtriangular, rather thin, compressed ante- 

 riorly, inflated over the mnbonial slope, which is pro- 

 foundly angulated and subrectilinear; posterior slope 

 flattened or slightly concave, much wrinkled; umbo 

 inflated, prominent, sloping anteriorly, distant from 

 the anterior margin; surface glabrous, olive-yellow; 

 within bluish; cardinal teeth double in each valve, 

 very oblique, compressed, elevated. 



SYNONYMES. 



U. ovatus, Say. Nicholson's Ency. (3d Amer. ed.) art- Conch. 



pi. ii. fig. 7. Lam. An. sans vert. vol. vi. p. 75. 

 Cab. J. N. S. No. 1225. 



OBSERVATIONS. 



The great depression of the posterior slope distin- 

 guishes this species from the cardium, Raf. Old 

 shells are produced posteriorly. It varies consider- 

 ably in form; some specimens are compressed, others 

 very ventricose, with rather broad radii over the 

 whole disk. This variety is so dissimilar to the 

 specimen figured, that I propose to designate it by 

 a distinct name, terming it variety ornatus; it is com- 

 mon in the rivers of South Alabama. The species is 

 common in the western waters. 



