Found 2 items, similar to Opisthobranchia.
English → English (WordNet) Definition: Opisthobranchia Opisthobranchia n : gastropods having the gills when present posterior to the heart and having no operculum: includes sea slugs; sea butterflies; sea hares [syn: subclass Opisthobranchia]
English → English (gcide) Definition: Opisthobranchia Opisthobranchia \O*pis`tho*bran"chi*a\, Opisthobranchiata \O*pis`tho*bran`chi*a"ta\, n. pl. [NL., from Gr. 'o`pisqen behind + ? gills.] (Zo["o]l.) A division of gastropod Mollusca, in which the breathing organs are usually situated behind the heart. It includes the tectibranchs and nudibranchs. [1913 Webster]