HERMIT CRAB, a genus of crustaceans (Paguridea) corn monly found on the coasts of Europe, America and the West Indies. In the adult stage it occupies the shells of gastropod molluscs, thrusting its abdomen inside the shell, the curve of which it follows ; this part of the body is not encased as in other species of the same order. It lives under commensal conditions by asso ciation with sponges, sea anemones and other animals. See CRUS