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The Orb Snails. Trumpet Snails

Genus PLANORBIS, Guettard

Shell a flattened, bi-concave, dextral coil, spire depressed; aperture small, rounded; margin simple, upper margin produced. Animal with short, ovate foot, short head and slender tentacles. Sluggish snails, in stagnant or slow running water. Distribution world-wide.

The Three-coiled Orb Snail (P. trivolvis, Say) is found in almost every pond, stream and ditch in this country, and should be popularly known. Its rounded coils increase with age, so the spire is at the bottom of a cup-like depression opposite the umbilical pit. Fine, close-set, knife-edged striations cross the whorls. The lip is callused within. Diameter, 1 inch.

Habitat.-Canada and United States.

P. campanulatus, Say, has a bell-shaped aperture. Length, 1/2 inch.

Habitat.-New England to Minnesota.

P. bicarinatus, Say, has two distinct keels and an enlarged aperture with angled lip. Diameter, 1/2 inch.

Habitat.-Canada to Kansas and Georgia.

Shells of Planorbis are delicate and easily warped in growth, so many monstrosities are found. Doubtless many named varieties are erected upon abnormal individuals.