NEW 

 FRESH WATER SHELLS 



UNIO POULSONI. 



Plate I. 



DESCRIPTION. 



Shell ovate, somewhat inflated, subalated, con- 

 nate, with a blackish epidermis, profoundly wrinkled 

 posteriorly; umbones not prominent; beaks hardly 

 elevated above the dorsal line; ligament margin 

 slightly arched; anterior side very short, and nar- 

 rowed; posterior side somewhat produced, and trun- 

 *'ated at the extremity; two obscure carinee radiate 

 I'rom the beaks behind the umbonial slope; region of 

 the umbonial slope inflated; anteriorly somewhat 

 <',ontracted and gaping at the base; cardinal teeth 

 directed obliquely backwards; very thick and sul- 

 cated; lateral teeth short; very distant from the car- 

 dinal teeth, and granulated; within dark purple; pos- 

 terior margin iridescent. 



