See text The Tonnidae are a family of medium-sized to very large sea snails, known as the tun shells.

During the day, they bury themselves in the substrate, emerging at night to feed on echinoderms (especially sea cucumbers), crustaceans, and bivalves.

Some larger species also capture fish, using their expandable probosces to swallow them whole.

Females lay rows of eggs that become free-swimming larvae for several months before settling to the bottom.

[3] This is in agreement with the action of Thiele (1925) who placed Tonnidae and Cassidae under "Tonnacea", therefore acting as first reviser under ICZN article 24.