Mr. Barnes on the Genera Unio and Alasmodonta, 263 



hind, sub-cylindrical, disks somewhat compressed ; anterior 

 side very much produced; beaks flat ; hgament elevated; 

 anterior dorsal margin depressed and flattened; basal mar- 

 gin nearly straight ; epidermis blackish brown, finely stria- 

 ted and deeply wrinkled transversely; naker purple of dif- 

 ferent shades, often with a purple centre and white margin. 

 Teeth crenate; lateral tooth rough, very thick, bending 

 downward, terminating abruptly and folded over towards 

 the interior of the shell. 



Remarks. — This shell in many respects resembles the 

 preceding, but it differs from it in being less, thicker in pro- 

 portion to the size, more attenuated before ; and it may be 

 distinguished from all others by the unusual thickness of 

 the lateral tooth. It is also more depressed immediately be- 

 hind the beaks, and the thickness of the anterior part of the 

 shell is very unusual, being in some specimens greater than 

 that of the posterior. In one specimen the lateral tooth of 

 the left valve measures two lines in thicknessi, and the chan- 

 nel of the opposite valve is two and a half lines broad. 



15. UNIO cuNEATus. — Shell ovate wedge-shaped, 

 thick, gibbous ; disks swelled, anterior lunule fur- 

 rowed ; lateral tooth thin ; inside purple. 



Inhabits the Ohio. Mr. S- B. Collins. 

 Mr. Collins's collection. 

 Diam. 1.6 Length 2.3 Breadth 3.8 



Shell elongated and sub-triangular, thick and ponderous; 

 anterior side narrowed, thin, angulate.d, wedge-shaped, 

 compressed ; umbones large and somewhat elevated; beaks 

 low and distant; anterior lunule long-heart-shaped, large, 

 distinct with an elevated ridge and longitudinally furrowed; 

 posterior lunule small and deep ; basal margin slightly 

 rounded; anterior margin narrow and augulated; anterior 

 dorsal, rapidly narrowed ; posterior dorsal impressed ; epi- 

 dermis blackish brown, somewhat ferruginous ; surface fine- 

 ly wrinkled, an elevated ridge extends from the beaks to the 

 anterior basal margin, and terminates in an angle on the 

 fore part. Cardinal teeth deeply divided and sulcated; lat- 

 eral tooth long, curved, and not very thick; cicatrices deep ; 

 cavity of the beaks small and not angular; naker brownish 

 purple, iridescent. 



