NEW FRESH WATER AND LAND SHELLS. 243 



Shell sparsely tubercuiate, triangular, rather inflated, subequilateral, emarginate behind, flattened at the 

 side; valves thick; beaks elevated; epidermis yellowish; cardinal teeth large; lateral teeth small and 

 straight; nacre white and iridescent. 



Hab. Holston River, East Tenn. Dr. Troost and S. M. Edgar. 

 My Cabinet, and Cabinets of Dr. Troost and Mr. Edgar. 

 Diam. .8, Length 1.3, Breadth 1.5 inches. 



Shell sparsely tubercuiate, 'triangular, rather inflated, subequilateral, emargi- 

 nate behind, flattened on the side from the beak to the margin, carinate on the 

 umbonial slope and sulcate posteriorly; substance of the shell very thick, thin- 

 ner behind ; beaks elevated ; ligament very short and rather thick ; epidermis 

 yellowish; cardinal teeth very large; lateral teeth very short and straight; 

 anterior cicatrices distinct; posterior cicatrices distinct; dorsal cicatrices 

 placed on the inferior part of the cardinal tooth ; cavity of the shell rather 

 deep ; cavity of the beak deep and angular ; nacre white and iridescent. 



RemarTiS. — Several specimens of this species have at diff"erent times been 

 brought to my attention by Dr. Troost and Mr. Edgar. I hesitated for some 

 time separating it from U. metanever^ Rafin., which in outline it closely resem- 

 bles, as well as in the arrow-headed markings. It may be distinguished from 

 that species by the size and rarity of its tubercles, having none of the large 

 ones on the umbonial slope which so well characterize the metanever. It is 

 also closely allied to U. tuherosus, (nobis,) but that shell differs in being thickly 

 covered with tubercles. 



Unio regularis. Plate 25, Fig. 59. 



Testa regulariter ellipticd, subinflatd, inaquilaterali; valvulis suhtenuihus ; natibus vix prominenti- 

 bus; epidermide luteo-fuscd, radiata; dentibus cardinalibus minutis, later alibus longis curvisque ; mar- 

 garita carulea et iridescente. 



Shell regularly elliptical, somewhat inflated, inequilateral; valves rather thin; beaks scarcely prominent; 

 epidermis yellowish brown, radiated; cardinal teeth very small; lateral teeth long and curved; nacre bluish 

 and iridescent. 



Hab. French Broad River, East Tenn. Dr. Troost and S. M. Edgar. 

 My Cabinet, and Cabinets of Dr. Troost and Mr. Edgar. 

 Diam. .8, Length 1.3, Breadth 2,3 inches. 



VIII. — 3 M 



