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Meaning of horseshoe crab

horse'shoe crab'

Pronunciation: [key]
  1. a large marine arthropod, Limulus polyphemus, of shallow coastal waters of eastern North America and eastern Asia, having both compound and simple eyes, book gills, a stiff tail, and a brown carapace curved like a horseshoe: a living fossil related to the woodlouse. Also called
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.