What is "trimusculus"

Trimusculus is a genus of medium-sized air-breathing sea snails or false limpets, marine pulmonate gastropod molluscs in the family Trimusculidae.

Trimusculus is the only genus in the family Trimusculidae. Trimusculidae, the button snails, is the only family in the superfamily Trimusculoidea, a superfamily of false limpets. These are marine pulmonate gastropod mollusks in the clade Eupulmonata.

Trimusculids are not very closely related to the siphonariids, another family of marine air-breathing false-limpets. The trimusculids are in the clade Eupulmonata, and are quite closely related to air-breathing land snails.