Shell. Oblong, slightly arcuated, thick, callous, and somewhat spiral on both sides, singular in formation, and its characteristic unlike most other shells. Inhabits the Isle of France. Two species.

2. Genus Aplysia. Pl. [X].

Animal. Body creeping, oblong, convex above; bordered on each side by a broad mantle, which covers the back when the animal is in repose; head and neck elevated, with four tentacula, the two upper ones ear-shaped, eyes situated near the mouth; dorsal shield semicircular, subcartilaginous, adhering on one side, and covering the branchial cavity.

Shell. Nearly round, left margin somewhat reflected; outer lip acute; yellowish horn colored, with brown radiations, and two concentric bands. Inhabits the Indian seas. Thirty-seven species.

FAMILY VI.
Limacina. Five genera.

1. Genus Limax. Pl. [X].

Animal. Cuvier merely mentions that the animal is “furnished with a coriaceous, subrogose shield, with a flat, longitudinal disk beneath; four tentacula retractile, eyes at the tips; orifice for respiration on the right side.”

Shell. Ovate oblong, both margins reflected; very thin, diaphanous, slightly wrinkled, of a pale yellow colour. Inhabits the gardens in Britain and France. Five species.