- Any of various marine arthropods of the class Merostomata, especiallyLimulus polyphemus or Xiphosura polyphemus of eastern North America, having a large, rounded body and a stiff, pointed tail. Also called king crab ,limulus 马蹄蟹，鲎：一种肢口纲的海生节肢动物，尤指产于北美东部的鲎目亚类 或 剑尾亚纲 ，体型大而呈圆形，尾巴尖而坚硬 也作 king crab,limulus