- horseshoe crab, king crab, Limulus polyphemus, Xiphosurus polyphemus - large marine arthropod of the Atlantic coast of North America having a domed carapace that is shaped like a horseshoe and a stiff pointed tail; a living fossil related to the wood louse
--1 is a kind of arthropod
--1 is a member of Limulus, genus Limulus