The family Cavoliniidae is a taxonomic group of small floating sea snails, pelagic marine opisthobranch gastropod mollusks.

[1] This family is part of a larger group which is commonly known as the sea butterflies because they swim by flapping what appear to be small "wings".

The parapodia are also covered with cilia, which produce a minute water current that pushes the planktonic food to the mouth of the animal.

The species may be globular, with both dorsal and ventral sides rounded, or bilaterally symmetrical with a long caudal spine.

The International Commission on Zoological Nomenclature (ICZN) has therefore changed the name back to its original spelling Cliidae Jeffreys, 1869, type genus Clio Linnaeus, 1767[4] Genus Clio Linnaeus, 1767 (synonyms: Cleodora Peron & Lesueur, 1810; Euclio Bonnevie, 1912 ) All species in this genus are characterised by a bilaterally symmetric, straight or adapically dorso-ventrally slightly curved shell, with an elliptical to triangular transverse section; protoconch clearly separated, globular or elliptical, frequently with a spine at the tip.