difference is so slight as not to be specific. Cuvier remarks 

 that " the female produces living young, which are found 

 in its oviducts, in the spring, in every state of develope- 

 ment. Spallanzani assures us, that the young, taken at 

 the moment of their birth and nourished separately, re- 

 produce without fecundation, like those of the Aphis. The 

 males are nearly as common as the females, their genera- 

 tive organ is exserted and retracted, as in Helix, by a hole 

 pierced in the right tentaculum, which causes this tenta- 

 culum to appear larger than tlie other. By this character 

 the male is easily known." 



The vivipara is far less common than the dedsa, and 

 seems to be more usually found in the southern part of 

 the Union. Mr. Elliott of Charleston sent me two speci- 

 mens from the banks of St. John's river, Florida, and Capt. 

 Leconte presented me with one, which he obtained at 

 Lake George on the same river. 



REFERENCE TO THE PLATE. 



The two middle figures exhibit the shell in two positioDB. 

 PLATE X. 



