subclass Opisthobranchia

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	Definition:		[n]  gastropods having the gills when present posterior to the heart and having no operculum: includes sea slugs; sea butterflies; sea hares
	Synonyms:		Opisthobranchia
	See Also:		class, class Gasteropoda, class Gastropoda, Gasteropoda, Gastropoda, Nudibranchia, order Nudibranchia