IN A‘SNAILERY. Y1 
sented by sandstone and volcanic rocks.* Hof springs are 
very likely to be inhabited by mollusks, even when the tem- 
perature exceeds 100° Fahr., and the waters are very strong- 
ly impregnated with mineral salts. 
Snails are mainly vegetarians, and all their mouth-parts 
and digestive organs are fitted for this diet. Just beneath 
the lower tentacles is the mouth, having on the upper lip a 
crescent-shaped jaw of horny texture, with a knife-like, or 
sometimes saw-like, cutting-edge. The lower lip has noth- 
ing of this kind, but in precisely the same attitude as our 
tongue is arranged a lingual membrane, long, narrow and 
cartilaginous, which may be brought up against the cutting- 
edge of the upper jaw. This “tongue” is studded with 
rows of infinitesimal silicious “teeth,” 11,000 of which are 
possessed by our common white-lipped helix, although its 
ribbon is not a quarter of an inch long. All these sharp 
denticles point backward, so that the tongue acts not only 
as a rasp, but takes a firm hold upon the food. On hold- 
ing the more transparent snails up to the light it is easy to 
see how they eat, and you can hear a nipping noise as the 
semicircular piece is bitten out of the leaf. Their voracity 
* See Dr. Hayden’s Report of the United States Geological Survey, 1874; 
and the Popular Science Monthly, July, 1875. 
