Mer·o·stom·a·ta prop. n. pl. 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.
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Merostomata
n : used in some classifications; includes the orders Xiphosura
and Eurypterida [syn: class Merostomata]