1?8 



HELICINA. 

 Lister, lab. 61, fig. 59. 



These shells in form greatly resemble the G.Nerita, 

 but are terrestrial, some feeding on trees, and others on 

 the surface of the earth ; they are also distinguished from 

 the G. Helix, by their transverse callous columella, de 

 pressed and diminished in thickness at the lower part. 

 Shell subglobular, not umbilicated; opening entire, 

 semi-elliptical, with a sharp edge, forming an angle at 

 the lower part or base of the right side; the operculum 

 is horny. The Trochus vestiarius of Linnaeus may be 

 confounded with this genus; but its being a marine 

 shell, and the callosity covering the whole of its lower 

 surface, by which it is rendered convex, sufficiently dis- 

 tinguish it from the Helicina, whose callosity is con- 

 fined to the columella side only. 



Helicina neritella Helicina fasciata 

 striata viridis. 



. 



