Trimusculidae

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Trimusculidae

Kingdom:	Animalia
Phylum:	Mollusca
Class:	Gastropoda
Subclass:	Orthogastropoda
Superorder:	Heterobranchia
Order:	Pulmonata
Family:	Trimusculidae Burch, J.Q., 1945

Genera

See text.

Trimusculidae is a family of small, air-breathing sea snails known as button shells, which are one kind of "false limpet". These are marine pulmonate gastropod mollusks.

They are in the order Eupulmonata, and as such they are related to air-breathing land snails.

Trimusculids are known as "button shells", because their shells are small, almost perfectly circular in outline, and white.

[edit] Shell description

The shells of these snails are somewhat limpet-like, but they are not at all closely related to the true limpets. They are air-breathing pulmonates, and can be distinguished from the true limpets by the presence of an internal lateral groove on the right side along with an interruption of the internal muscle scar ring. These shell features corresponds to the positioning of pulmonary orifice. These distinguishing shell characters are not as noticeable as they are in the shells of the Siphonariidae.