VALVATA PUPOIDEA. 11 



nut-colored, when divested of the rough, dirty 

 pigment which usually adheres closely to it; 

 whorls four or five, minutely wrinkled, the pos- 

 terior one small and flattened so as to form an 

 obtuse apex; the others cylindrical, and so par- 

 tially in contact as to expose about one-half of 

 the cylinder; the last entirely disjoined from the 

 preceding one for at least the half of a revolu- 

 tion [in the adult]; aperture circular, lip simple 

 and sharp; on looking at the shell from below, 

 no umbilical opening is found; operculum horny, 

 apex central, elements concentric. Length one- 

 tenth, breadth three-fortieths inch." Gould. 



GEOGRAPHICAL DISTRIBUTION. Found in ponds 

 in the vicinity of Boston, Massachusetts, ad- 

 hering to submerged sticks and stones. 



OBSERVATIONS. 



In its immature state, before the body whirl 

 is detached, this species cannot be distinguished 

 from Amnicola, except by the opercle, and the 

 slightly ovate aperture adds to the deceptive 

 character of the shell. The separation of the 

 last whirl deprives the shell of a proper umbilic. 



