- Nudibranchia, order Nudibranchia - comprising numerous marine gastropod mollusks lacking a shell in the adult state and usually having a body like a slug
--1 is a kind of animal order
--1 is a member of Opisthobranchia, subclass Opisthobranchia
--1 has members:sea slug, nudibranch; Aplysiidae, family Aplysiidae, Tethyidae, family Tethyidae; Hermissenda, genus Hermissenda