Opisthobranchia(redirected from Opistobranch)
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|Noun||1.||Opisthobranchia - gastropods having the gills when present posterior to the heart and having no operculum: includes sea slugs; sea butterflies; sea hares|
Nudibranchia, order Nudibranchia - comprising numerous marine gastropod mollusks lacking a shell in the adult state and usually having a body like a slug
class - (biology) a taxonomic group containing one or more orders