Large marine arthropod of the American Atlantic coast having a domed horseshoe-shaped carapaceand stiff pointed tail; a living fossil related to the wood louse.

• 美洲大西洋海岸的大型海生节肢动物,有半球形马蹄状甲壳和硬而尖的尾巴;与林虱有关的一个活化石。