The Shield Snails River Limpets

THE SHIELD SNAILS. RIVER LIMPETS Genus ANCYLUS, Geof.

Shell patelliform, not spiral, thin; apex sinistral; jaws, three; radula broad, crowded with teeth; foot large; mantle included; tentacles triangular; pulmonary orifice protected by a flap. A. rivularis, Say, has a horny, opaque shell, with blunt, sub-central apex. The large, oval aperture narrows at one end.

Lining white. This is found adhering to stones in rivulets. Length, f inch.

Habitat.—Massachusetts, Virginia, Wisconsin.

A. Newberryi,

Lea, is a large blunt dome, smoky red, with sides somewhat compressed, making an elliptical aperture. This is easily the largest species in the genus. Length, i inch.

Habitat.— Lake Klamath, Cal,