43 



UN 10 ALTILIS. 



Plate U.~Fig. 1. 



DESCRIPTION. 



Shell suboval, thin, inflated; beaks slightly promi- 

 nent and much decorticated; posterior margin suban- 

 gulated; nmbonial slope rounded, behind which is an 

 obscure rib declining from the beaks to the posterior 

 extremity; base arcuated; epidermis blackish, rugose, 

 olivaceous over the umbones and rayed; and with 

 numerous short vermicular lines on the posterior 

 slope; cardinal teeth subpyramidal, erect; lateral 

 teeth distant; a profound elongated muscular impres- 

 sion on the callus; nacre whitish and iridescent. 



OBSERVATIONS. 



Inhabits the Alabama river, near Claiborne, and is 

 rather rare. Young specimens resemble in outline 

 the U. multiradiatus, Lea. Old shells have the epi- 

 dermis almost black. 



UNIO PEROVALIS. 



Plate l\.—Fig. 2. 



DESCRIPTION. 



Shell oval, moderately thick, inflated; beaks promi- 



