HELIX. 257 



depressed, having within, a single tooth on thebase ; lip 

 simple, thin. 



Greatest transverse diameter three-eighths of an inch. 



Geographical Distribution. Inhabits the "Western 

 States, and was noticed by Mj*. Say in the North-western 

 Territory. Mr. Bartlett found it in Tennessee, Ken- 

 tucky, Arkansas, Georgia, and Virginia. It is commonly 

 supposed to exist in Massachusetts and other New Eng- 

 land States ; but, so far as my own observation extends, 

 it is replaced in those States by Helix striatella, which 

 it very much resembles. 



Remarks. This is a common shell in those parts of 

 the country which it inhabits. In Ohio it is particularly 

 abundant, vast numbers of them being sometimes found 

 under the bark of a single decaying tree. The striae 

 of increase on the upper sm-face are remarkably promi- 

 nent, and almost angular, and serve to distinguish it from 

 every other species ; on the lower surface they are very 

 distinct, but less prominent, and the direction of their 

 curve is the reverse of that above : they converge into 

 the umbilicus. It varies considerably in size, and young 

 shells are often carinated. In mature individuals there 

 is a single, sub-prominent tooth on the base of the shell, 

 within the aperture. Some specimens are entirely white ; 

 and, though thus bleached and deprived of color in the 

 shell, the animal seems to be healthy and active. 



It resembles Helix rotundata, Miiller, but is destitute 

 of the alternate markings of that species. There cannot 

 VOL. II r 65 



