limulus(n = noun.animal) genus limulus - type genus of the family Limulidae;
is a kind of arthropod genus
is a member of family limulidae, limulidae

   The only existing genus of Merostomata. It includes only a few species from the East Indies, and one (Limulus polyphemus) from the Atlantic coast of North America. Called also Molucca crab, king crab, horseshoe crab, and horsefoot. [1913 Webster]

genus limulus, limulus polyphemus