Aplysia

Aplysia, the Sea Hare, a slug-like gastropod (q.v.) with a thin transparent internal shell. It lives among seaweed below the low-tide line. It is the type of the family Aplysiadae, which belongs to the Opisthobranchiate (q.v.) group of the Aplysiadae, a family of Gastropods, as the breathing organs (branchiae) are situated behind the heart.