Cavoliniidae: Cavolinia tridentata (Forsskål in Niebuhr, 1775) (‘three-toothed sea-butterfly’)
Synonym(s): tridentata Forskal, 1950.
Typical shell-length 20 mm. Lives in offshore waters in midwater. Native. Occurs in eastern and western Australia (QLD, NSW, TAS and WA); also widespread in cool temperate zones of both hemispheres.