84 HELICID^. 



the whole animal may retire. Head obtuse, without a 

 constricted neck. Tentacles four, retractile, the supe- 

 rior long, slender, terminating in an ocuhferous bulb ; 

 inferior one short, delicate, but always conspicuous. 

 Lip simple, mouth inferior, armed with a transverse cor- 

 neous jaw, and containing a lingual organ beset with 

 ranges of numerous hooks or denticles. * 



Shell. Form variously discoidal, globose, or conical, 

 the axis seldom equalling the diameter. Aperture gen- 

 erally longitudmal, obhque, circular, lunate or ringent ; 

 lip simple or reflexed, not continuous, though often con- 

 nected by a deposition of enamel ; columella continuous 

 with the curve of the lip ; throat simple or armed with 

 denticles or lamma. Base perforated or imperforate. 

 Surface without varices or deep sculpture. 



Geographical Distribution. This genus inliabits 

 every part of the territory of the United States, as it 

 does every region of the earth where land shells of any 

 kind are found. It may well be called cosmopolite. 

 The genus Vitrina alone, may perhaps extend to some- 

 what higher latitudes and altitudes. 



Remarks. The genus Helix, as originally constituted 

 by Linnaeus, embraced not only all the Helicidae, but also 

 all the fresh-water univalves, and even some marine 

 genera. It has been successively amended by various 

 authors, especially by Miiller, Lamarck, and Draparnaud, 

 so that at least a dozen well characterized genera have 



