338 J^ew species of Fresh Water Shells. 



Art. IX. — Description of some New Species of Fresh Water Shells 

 from Alabama, Tennessee, &fc. ; by Timothy A. Conrad, Mem- 

 ber of the Academy of Natural Sciences of Philadelphia. 



Unio ccelatus. pi. 1. fig. 2. 



Shell sub-triangular ; much compressed, surface waved and with 

 small irregular undulations becoming profound towards the posterior 

 margin; anterior side and umbo destitute of undulations; umbones 

 flattened ; beaks prominent. 



Inhabits Tennessee, Elk and Flint rivers, and is rare. Length 

 1.8 inches. Cabinet of the Academy of Natural Sciences of Phil- 

 adelphia. 



Shell sub-triangular; very inequilateral, and much compressed, 

 with a broad furrow extending from the beaks to the base ; an- 

 terior sides and umbo entire, and the remaining parts furnished with 

 small irregular interrupted undulations, which are profound behind 

 the umbonial slope ; surface rough, with distant slight concentric 

 grooves; umbones much flattened; beaks prominent, compressed; 

 epidermis dark olive, and obscurely rayed; cardinal and lateral teeth 

 very robust; anterior and posterior muscular impressions profound; 

 nacre pearly white and iridescent. 



Observations. This is a remarkable and very distinct species; 

 very similar in outline to the U. securis of Lea ; but differing from 

 all its congeners in the singular manner in which its undulations or 

 incipient tubercles are disposed ; it is nearly as much compressed as 

 the U. securis. The epidermis in some specimens is almost black. 



Unio perovatus. PI. 1. fig. 3. 



Shell ovate, ventricose, valves moderately thick; beaks rather 

 prominent, cardinal teeth erect ; lateral teeth rectilinear, compress- 

 ed ; nacre white. 



Inhabits Prairie creek, Marengo Co. Al. rare; Length L9 inches. 

 Cabinet of the Academy of Natural Sciences of Philadelphia. 



Shell ovate, rather ventricose, valves thick on the anterior side, 

 but becoming much thinner on the posterior ; anterior margin regu- 

 larly rounded ; basal margin rounded ; posterior extremity subangu- 

 lated ; beaks a little elevated, approximate and undulated at tip; 

 epidermis olive, and wrinkled towards the margin ; cardinal teeth 

 erect and prominent, not very thick ; lateral teeth rectilinear, com- 



