12 



UNIO FRAGOSUS. 



Plate VI. Fig. 2. 

 DESCRIPTION. 



Shell suborbicular, ventricose, with an indistinct 

 narrow furrow, and two approximate series of very 

 prominent irregular tubercles, anterior ones largest; 

 umbonial slope angular; posterior slope slightly con- 

 cave, with a few narrow rib-like tubercles, more pro- 

 minent near the margin; posterior margin direct, 

 slightly emarginate; ligament slope straight, slightly 

 oblique; umbo narrow, prominent; beaks much in- 

 curved, pointed, tuberculated; epidermis brown, with 

 two or three broad, widely interrupted green rays. 



OBSERVATIONS. 



This fine spocies approaches quadridus, Raf., but 

 is much more ventricose, has more prominent tuber- 

 cles, and is very distinct. I am indebted to Dr. 

 Blanding for the splendid specimen represented by 

 the figure; it is from the Scioto river, Ohio. 



