Merostomata
Merostomata , proper noun, plural
[New Latin, from Greek me`ros thigh + {not transcribed}, -{not transcribed}, mouth.]
(Zoology) 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.