The living snails and shells of the Berlin area described by the insect researcher Johann Philip Emil Friedrich Stein in 1850. Illustrated with 73 black and white images on 3 plates. Snails (Gastropoda, Greek for "stomach foot") are a class of animals within the phylum Mollusca. It is the most species-rich of the eight extant classes of mollusks and the only one that has also produced terrestrial species. The body size of adult snails varies from under 0.5 mm (family Omalogyridae) to 75 cm (Aplysia vaccaria). The shell known as the snail shell consists, like that of other shelled mollusks, of calcium carbonate, but differs significantly in its asymmetrical spiral coiling, allowing it to be distinguished from the shell of a bivalve, for example. Reprint of the original edition from 1850.