Cymbulioidea

Cymbulioidea is a taxonomic superfamily of pelagic "sea butterflies", one group of swimming sea snails. They are holoplanktonic opisthobranch gastropod molluscs in the clade Thecosomata.

==Anatomy== Some groups within this superfamily possess a shell in the adult stage, some are without a shell in the adult stage, and others have developed a relatively tough gelatinous, cartilaginous internal structure, a sort of fake shell called the pseudoconch.