horseshoe crab
noun
1- a large marine arthropod with a domed horseshoe-shaped shell, a long tail-spine, and ten legs, little changed since the Devonian鲎。
1.1
- Class Merostomata, subphylum Chelicerata: four species, in particular the North American Limulus polyphemus.肢口纲, 有螯肢亚门：4种, 尤指北美鲎（拉丁名 Limulus polyphemus）。