116 HELICIDJE. 



middle of the lowest volution and continues round 

 the base of the rest, not penetrating the aperture : 

 this band is often faint, rarely wanting; aperture 

 seinielliptic, longer than wide, produced at the pillar 

 side, with the margin slightly reflected and white, 

 with a white internal rib. 



The young shells have a thin lip, with a slight 

 white internal rib. 



It varies 1. In colour, from dark chestnut to 

 pale yellowish white, with only a few whiter specks. 



2. In the thickness of the shell, the thinner speci- 

 mens being generally destitute of the band. 



3. In the presence or absence of the band. 



4. In the size, according to the locality. The 

 small mountain variety has been called a species by 

 the Swiss shell dealers. 



It is sometimes distorted 1. by the whorls being 

 reversed ; 2. the spire more or less elevated or 

 depressed ; 3. very rarely the whorls are elevated 

 and separated from one another. (See Ftrus. Hist. 

 t. 29. f. 1, 2, 3.) 



d. Shell subdiscoidal, above flat, beneath umbilicated ; 

 brown, one-coloured; mouth trigonal, edge more or 

 less toothed ; periostraca hispid, with long hairs. 

 (Trigonostoma Fitz.) 



40. 7. HELIX obvoluta. Cheese Snail. Shell or- 

 biculate, flat umbilicated, bald, reddish brown; 

 spire rather concave ; mouth triangular, edge 

 slightly reflexed, with a small tooth on the in- 

 side of the lip; lips reddish white, (t. 11. f. 

 131.) 



