a suborder of mollusks lacking a shell in the adult and having external respiratory appendages usually on the dorsal surface.

Order Nudibranchia ("naked gill") a shell-less snail in the mollusk family, having have outer gills in the form of featherlike appendages surrounding the anus (called anal gills). Nudibranchs also have a pair of rhinopores (sensory tentacles) on their heads.

is another name for a sea slug. Sea slugs are often flamboyantly colored.

any of various marine gastropods of the suborder Nudibranchia having a shell-less and often beautifully colored body