NEW FRESH WATER AND LAND SHELLS. 199 



Shell elliptical, much compressed, very inequilateral ; valves thin; beaks rather prominent; epidermis 

 yellowish brown ; cardinal teeth small; lateral teeth long and rather curved ; nacre white and iridescent. 



Hab. Big Pigeon River, Tenn. S. M. Edgar. 



My Cabinet. 

 Diam. .7, Length 1.3, Breadth 2.1 inches. 



Shell elliptical, much compressed, very inequilateral, subbiangulate behind; 

 substance of the shell thin, thicker before; beaks rather prominent; ligament 

 long and thin; epidermis yellowish brown and obscurely rayed; cardinal teeth 

 small, single in the right and double in the left valve; lateral teeth long and 

 rather curved; anterior cicatrices distinct; posterior cicatrices confluent; dorsal 

 cicatrices placed under the plate between the lateral and cardinal teeth; cavity 

 of the shell very shallow ; cavity of the beaks very shallow and angular ; nacre 

 white and very iridescent on the posterior part. 



Remarks. — A single specimen only of this species was taken by Mr. Edgar. 

 In outline it nearly resembles U. radiatus, but is a thinner and flatter shell and 

 with very indistinct rays. 



tJNio Tennesseensis. Plate 10, Fig. 11. 



Testa ellipticd, transversa, injlatd; valvulis crassis; natibus subprominentibus;' epidermide luted; 

 dentibus cardinalibus magnis erectisque; later alibus magnis subcurvisque ; margaritd alba etiridescente. 



Shell elliptical, wide, inflated; valves thick; beaks rather prominent; epidermis yellow; cardinal teeth 

 large and erect; lateral teeth large and somewhat curved; nacre white and iridescent. 



Hab. Stone's River, Tenn. S. M. Edgar. 



My Cabinet. 

 Diam. 1.3, Length 1.9, Breadth 3 inches. 



Shell elliptical, wide, inflated, more full over the umbonial slope; substance 

 of the shell thick, thinner on the posterior portion; beaks rather prominent; liga- 

 ment rather long; epidermis yellow, without rays, and coarsely wrinkled; 

 umbonial slope very round; cardinal teeth large, erect, pointed, double in the left 

 valve and single in the right; lateral teeth large, rather long, slightly curved 

 and separated from the cardinal teeth; anterior cicatrices distinct; posterior 

 cicatrices distinct; dorsal cicatrices large and placed in the centre of the cavity 

 vin. — 3 A 



