72 



Jefferson county, New York, where the species is 

 extremely abundant. 



UNIO CAPS^FORMIS. 



Plate XL. — Fig. 2. 

 DESCRIPTION. 



Shell sub-oval, slightly ventricose, moderately 

 thick; posterior side flattened or very slightly grooved; 

 umbonial slope obtusely angulated; basal margin 

 rounded medially, straight or slightly emarginate 

 posteriorly; posterior extremity direct, truncated, 

 narrowed, slightly produced; summits obtusely round- 

 ed, not prominent; epidermis yellowish, with nume- 

 rous narrow unequal green rays; within white; cardi- 

 nal teeth very erect and prominent. 



SYNONYME. 



U. caps.eformis, Lea. Trans. Amer. Philos. Soc, new series, 



vol. iv. p. 143, pi. ii. fig. 4. 

 Cab. A. N. S. No. 20414. 



OBSERVATIONS. 



Inhabits Cumberland river near Nashville, Tennes- 

 see. I have found it in the Tennessee river at Flo- 

 rence, Alabama. It bears a slight resemblance to 

 the young of U.flexuosas, and is a very distinct spe- 

 cies. The female is represented in figure 3. Be- 

 tween the sexes the difference in outline is greater 

 than in any species with which we are acquainted, 

 except U. gibbosus, Raf. 



