not consider it a variety of any hitherto described. 

 The figure represents one of the largest specimens 

 which I found. 



UNIO FURVUS. 



Plate W.—Fig. 3. 



DESCRIPTION. 



Shell oval, ventricose, thickbefore, thinner behind, 

 posterior margin wide, hardly angulated; umbonial 

 slope angulated, behind which is an obscure impress- 

 ed line; epidermis almost black, with minute crowded 

 wrinkles; cardinal teeth slightly oblique, pyramidal; 

 within white, highly iridescent on the posterior 

 margin. 



OBSERVATIONS. 



A species which I found in the Black Warrior 

 river, in company with the preceding; it is very rare. 



UNIO RAVENELI. 



Plate W.'—Fig. 4. 



DESCRIPTION. 



Shell oblong oval; ventricose; beaks hardly promi- 

 nent; ligament margin straight, not obhque; base 

 very slightly arcuated; umbonial slope angulated, 



