8 VALVATA SINCERA. 



two-thirds as wide as the last whirl; margin of 

 the aperture touching the penultimate whirl. 

 Length 0.1; breadth 0.2 inch; divergence of the 

 spire about 135." Adams. 



GEOGRAPHICAL DISTRIBUTION. Inhabits the 

 Northwestern Territory and Vermont. 



OBSERVATIONS. 



"This shell is much like the var. SIMPLEX of 

 the preceding species. The umbilicus is usually 

 a little larger, but the most striking character- 

 istic is the rapid enlargement of the whorls, the 

 last being more than three times the diameter 

 of the penultimate. The divergence of the 

 spire is never so small as in that species, but 

 like that, is sometimes much more than in the 

 type of the species, even to 180." Adams. 



