Sphincterochila zonata zonata
Sphincterochila zonata zonata is a subspecies of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Sphincterochilidae. This species lives in deserts in Israel and Egypt. Helix boissieri is the type species of the genus Sphincterochila. The type species was subsequently designated by Henry Augustus Pilsbry in 1895. It is named after botanist Pierre Edmond Boissier. Sphincterochila zonata zonata lives in the Negev desert (Israel), and the Sinai desert in the Sinai Peninsula (Egypt). Shell description Shell is cretaceous, white; consists of five convex whorls and a deflected ultimate whorl. The aperture is thickened, projecting internally in two subconcrescent denticles (described by Tryon as "tubercles"). The average diameter of the shell is 25 mm. Anatomy and physiology The average body mass of Sphincterochila zonata zonata is around 4.3 g. Such mass is approximately divided in an even manner between the shell itself and the animal's soft parts. Schmidt-Nielsen et al., in 1971, found that 56% of the animals body mass was contained in its shell. About 80 to 90% of the mass of the soft body parts is composed of water (according to the Yom-Tov 1970). In average, soft body parts contain 81% of water (nearly 1400 mg