Synonyms for Horseshoe Crab (same or very similar meaning)
WordNet sense 1 (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):
king crab, Limulus polyphemus, Xiphosurus polyphemusFrom the ODE community, based on WordNetadd/edit