Chiton, a genus of marine animals, generally arranged as a family of gasteropod mollusks. The shell is composed of eight transverse imbricated plates, attached to a thick mantle which forms an expanded margin around the body; the border of the mantle is either bare or covered with minute plates, hairs, or spines.
Chiton squamosus and C. spinosus.
The animal has a broad creeping disk, like the limpet; no eyes, no tentacles, but a long linear tongue in a cartilaginous proboscis, well armed with teeth. Heart central, and elongated like the dorsal vessel in annelids; sexes united; intestine straight, and anal orifice posterior and median. The name is derived from the resemblance of the shell to a coat of mail (Gr. ). More than 250 species are known, occurring in all climates, throughout the world; most abundant on rocks at low water, but some live at a depth of 100 fathoms; they have existed from the Silurian period. It is an aberrant form of mollusk, and some are inclined to place it rather among articulates, or at least as a form leading to the articulates. Some of the tropical species grow to a large size, and their muscular foot is often used as food.