King crabs, also called stone crabs are a family of crab-like decapod crustaceans chiefly found in cold seas. Their large size means that many species are widely caught and sold as food. King crabs are generally believed to be derived from hermit crab ancestors, which may explain the asymmetry still found in the adult forms. Although some doubt still exists about this theory, king crabs are the most widely-quoted example of carcinization among the Decapoda.
McLaughlin, P. A. (1993). Illustrated keys to families and genera of the superfamily Paguroidea (Crustacea: Decapoda: Anomura), with diagnoses of genera of Paguridae. Memoirs of Museum Victoria 60(1): 111-144
The term king crab is also sometimes used of the horseshoe crab Limulus.