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 umbonial 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. A. 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. 



