Merostomata

‖prop. n. pl. [ NL., fr. Gr. me`ros thigh + &unr_;, -&unr_;, mouth. ] (Zool.) A class of Arthropoda, allied to the Crustacea. It includes the trilobites, Eurypteroidea, and Limuloidea. All are extinct except the horseshoe crabs (Limulus) of the last group. See Limulus. [ 1913 Webster ]