138 



ture is nearly the same, the umbilicus of that species is 

 never closed, and it never attains the size of the present 

 species. The lower lip-tooth is also very different. 



Varieties of the type are caused by the absence of the 

 upper or lower lip-tooth, or of both, the want of the raised 

 projections of the epidermis, and of the transverse striae, 

 and by the great depression of the spire in some individ- 

 uals, which produces a distinct angle or carina on the 

 outer whorl. This last variation brings it within the 

 genus Carocolla of Lamarck, and shows that the dis- 

 tinctive characters of that genus are of no value. 



A carinate variety, which was noticed by Mr. Say as 

 " a variety with a very prominent, acute carina, destitute 

 of minute protuberances," and having the carina crenu- 

 lated by prominent transverse striae, has been described 

 by Mr. Lea as Carocolla helicoides. It is the same 

 figured by Ferussac, pi. 50, a. fig. 7. 



A carinate striate variety with smooth epidermis, was 

 described by Mr. Say as Helix obstrieta. 



Another variety, having the oblique striae widely 

 separated, and very distinct, and being at the same time 

 somewhat carinate, has been described by Mr. Lea as 

 Helix Carolinensis. An inspection of the shells from 

 which these descriptions were made has convinced me 

 that they are only varieties of this species. 



A singular variety is found in the neighborhood of 

 Vicksburgh, Mississippi, in which the lip, though thickened 

 and white within, is scarcely reflected, but forms a con- 

 tinuous line with the last whorl. Instead of being ap- 



