Wormlike holothurians with rough or warty surface, without tubefeet (except on tetacles). Body wall very thin. Without anal papillae, respiratory trees, and tetacle ampullae. Simple, digitate or pinnate tentacles (10-25). Ossicles absent in a few species, but usually including anchors, anchor plates, or wheels. Species usually small, upto a few centimetres; some tropical species, however, can reach a length of 2 m. Larval stages usually pelagic, but some species are viviparous. Apodids usually live under rocks or burrowing in the sand in shallow water.