Velutin Snail

Description

The color of the body may vary from uniformly velvety black to brown. The mantle is broadly tuberculate. The borders of the mantle are delicate, notched in front and spreading out widely. The foot is small and oval. There are four or five lobes or bosses on the dorsal part of its body.

There is an inhalant siphon extended in the middle of the front part of the body. The tentacles are triangular, granulated and are spotted with white. There are brown eyes at the base of the tentacles. The front part of the foot is grooved. There is a jaw and a radula with 48 teeth in the mouth.

The body length is usually about 80 mm.

C. nigra has an internal and reduced shell, and spirally rolled radula, as have all the members of the family Velutinidae. The shell is conchinous and it has 2½ or three whorls. Whorls are expanding rapidly and the last whorl cover four fifths of the shell height. The color of the shell is translucent white. The shell is smooth with irregular growth lines. The aperture is large. Shell width is 6.3 mm (for a shell length of 10 mm). Shell length varies from 10 mm to 30–40 mm.

Distribution

The distribution of Coriocella nigra is Indo-Pacific and includes South Africa, Mozambique, Kenya, Madagascar, Mauritius, Réunion, Mayotte, Gulf of Aden, Gulf of Elat, South Button Island, Myanmar, Thailand, Indonesia, Papua New Guinea, northern Australia and eastern Australia, Philippines, Palau, Society Islands in French Polynesia, New Caledonia, Japan, and Hawaii.

Habitat

It lives on rocky habitats. On Hawaii it lives among Halimeda kanaloana. In Australia it inhabits intertidal and subtidal zone. It has been reported from depths of 1–4 m,[20] to 12 m and to 15 m.
C. nigra is carnivorous. Its probable prey are tunicates, including tunicates from the family Didemnidae in Hawaii.

The ostracod Pontocypria coriocellae lives as an occasional commensal in the oral tube of C. nigra.
The shell of C. nigra is sometimes used by a hermit crab, Clibanarius virescens.