2. Genus Pleurotoma. Pl. [XI].

Animal. Body oval, spiral above, enveloped in a mantle of which the right edge is furnished with lobes; foot oval and somewhat short; eyes situated at the external base of long, conical, retractile tentacula; mouth having a long extensible proboscis armed with hooked teeth; organs of respiration formed by two unequal branchiæ.

Shell. Fusiform, a little wrinkled, with a turriculated spire; a small oval aperture, terminated by a straight canal more or less long, with the right edge trenchant; a horny operculum. Distinguished from the Cerithium by having a notch in the margin. Twenty-nine living species. Thirty fossil.

3. Genus Turbinella. Pl. [XI].

Animal. Imperfectly known.

Shell. Usually turbinated (but sometimes turriculated), wrinkled, thick; spire slightly variable in form; aperture elongated, terminated by a straight canal, and often rather short; the left edge nearly straight and formed by a callosity concealing the columella, which has two or three nearly transverse and unequal folds; the right edge entire and trenchant. Found in the Equatorial or Australian seas. Twenty-three species.

4. Genus Cancellaria. Pl. [XI].