The members of the Cadlinidae family have only recently been extracted from the Chromodorididae family and the composition is not entirely settled. The family is defined by internal characters, and externally cadlinids resemble small members of the Dorididae, Discodorididae or Chromodorididae.
In general, the Cadlinidae has an ovate shape that can be elongated when crawling. The dorsum is convex in profile. The mantle is larger than the foot and completely covers the animal except in some species where the posterior tip of the foot is exposed. The mantle tissue contains spicules giving it a toughened appearance. The mantle usually also possesses low rounded tubercles on the surface and many microscopic glands scattered all over. Some species also have large sub-marginal mantle glands.
The rhinophores are lamellate and can retract into separate pockets. The simple, sometimes complex, gills form a circle around the anus and are able to retract into a pocket beneath the mantle.
Generally the Cadlina are plain in appearance being white or pale coloured sometimes with a coloured mantle margin and gill and rhinophore pockets. The Cadlina are usually found in temperate to polar zones, though the Aldisa species are tropical and somewhat more colourful.