HELIX. 165 



Greatest transverse diameter, three-fourths of an inch. 

 Common size half an inch. 



Geographical Distribution. This species has 

 been noticed in Michigan, Vermont, New York, Vir- 

 ginia, Georgia, Tennessee, Qhio, Illinois, Missouri, and 

 the North-western Territory. It may, therefore, be con- 

 sidered to inhabit the whole territory of the United 

 States. 



Remarks. This shell, though frequently seen, does 

 not seem to be so numerous in our forests as some other 

 species. It is peculiar for the elegant, rounded shape 

 of the whorls, as seen on their lower surface. It rarely 

 varies from the common type, and cannot be mistaken 

 for any other species, with the exception hereafter men- 

 tioned. The animal is voracious in its appetite, almost 

 always preying upon other species with which it may be 

 kept, and so certainly destroying them that I have been 

 obliged to keep them by themselves. This they effect 

 by inserting their narrow bodies, which they have the 

 power of elongating and protruding very far from their 

 own shells, into the shells of their victims, and then feed- 

 ing upon them at their leisure. It burrows in the soil 

 under decaying logs. 



The earliest description of this shell was by Mr. Say, 

 in 1821, under the name of H. concava. F^russac 

 noticed it (without description or figure) in 1822, as 

 H. planorboides, and some years afterwards gave a 

 figure of it under the same name. Mr. Say's name has 

 VOL. II. 42 



