The Orb Snails Trumpet Snails

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.

29 The Pond Snails 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 um bilical pit. Fine, close-set, knife-edged striations cross the

whorls. The lip is callused within. Diameter, I inch.

Habitat.— Canada and United States.

P. campanulatus,

Say, has a bell-shaped aperture. Length, i inch.

Habitat.— New England to Minnesota.

P. bicarinatus,

Say, has two distinct keels and an enlarged aperture with angled lip. Diameter, i 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.