This is a fresh-water shell, found in the lakes of Europe.

Shell thin and brittle, obliquely conical; summit pointed and recurved; margins simple, base oval and smooth.

Ancylus oblongus.

Ancylus fluviatilis.

A. oblongus. The oblong Ancylus.

Aperture elongated, vertex turned to one side, striated concentrically; exterior pale yellowish colour, interior light blue.

A. fluviatilis. The river Ancylus. Pl. [32], fig. 3.

Simple, oval, almost symmetrical; summit pointed, compressed, very distinct; bent back a little to the right, but not marginal; the edges of the aperture entire and effuse.

FAMILY IV.
Bullacea. Three genera.

1. Acera. Has no shell. One species.