Mr. Barnes on the Genera Unio and Alasmodonta. 259 



external surface is neither waved nor tuberculated. The 

 teeth are less sulcaiedthan those of the former, and only cren- 

 ulated, or striated, generally triangular and elevated, aivi, in 

 magnitude., bear a proportion to the thickness of the shell. 

 The cavity of the beaks is small, or none, and neither angu- 

 lar nor compressed. The shells have a smooth and regular 

 appearance, and Jive of the seven species have the inside pur- 

 ple. 



SPECIES. 



(a. outline 



10. UNIO ELLIPTICUS. Fig. 19. <;| ' ^ 



\^d. sizes. 

 Shell regularly oval, thick, convex, glabrous, beaks 

 depressed. Teeth elevated, triangular, striated. 



Unio Crassus. Mr. Say. Plate 1 fig. 8 ? 



Mya Complanata .^ Dilhcyn,. page 51. 



Inhabits Fox River. Mr. Schoolcraft. 

 Dr. Mitchill's Cabinet. 

 My Collection. 

 Diam. 1.0— 2.0 Length 1.7— 3.2 Breadth 2.5— 4.9 inches. 

 Shell long before, and short behind, equally rounded at both 

 extremities; beaks nearly flat; ligament elevated above the 

 beaks; epidermis yellowish brown, obscurely rayed, rays 

 disappearing in old specimens ; slightly flattened on the an^ 

 terior slope ; teeth deeply divided, elevated, finely striated ; 

 anterior cicatrix wrinkled ; posterior rough ; cavity of the 

 beaks considerable. Maker pearly white, iridescent, and 

 sometimes, of a beautiful flesh colour. 



11 TT- in ^ «• inside. 



11. UNIO CARINATUS. hl^. 10. < , ^ ., 



^ lb. outside. 



Shell oblong oval, biangulate before, rayed, hinge 

 margin straight, compressed, keel-shaped, teeth 

 finely striate. 



^ 



Inhabits Fox River. Mr. Schoolcraft. 

 Dr. Mitchill's Cabinet. 

 My Collection, 



