Definition
A snail is any of the approximately 74,000 species in the class Gastropoda of the phylum Mollusca or, alternatively, any of the 12 or so species of land pulmonate gastropods used as human food.
Etymology. O.E. snęgl, from P.Gmc. *snagilas (cf. O.S. snegil, O.N. snigill, M.H.G. snegel, dial. Ger. Schnegel, O.H.G. snecko, Ger. Schnecke "snail"), from base *snag-, *sneg- "to crawl" (see snake). The word essentially is a dim. form of O.E. snaca "snake," lit. "creeping thing." Also formerly used of slugs. Symbolic of slowness since at least c.1000; snail's pace is attested from c.1400.
Discussion
Some eat both plant and animal matter; others eat only one type of food. Snails in Hawaii are associated with feeding injury to a wide range of plants.
In feeding, all snails use a characteristic rasping tongue or radula. This is a chitinous ribbon bearing teeth which is moved over a supporting protrusible “tongue” with a to-and-fro action. The radular apparatus has a twofold function: it serves both for rasping off food material (mechanically like an inverted version of the upper incisor teeth of a beaver) and for transporting the food back into the gut like a conveyor belt. Although some land snails cause economic losses by destroying vegetation, even more harm is done to gardens by slugs.