Source : Webster's Revised Unabridged Dictionary (1913)

Merostomata \Mer`o*stom"a*ta\, n. pl. [NL., fr. Gr. ? thigh + ?,
   -?, mouth.] (Zo["o]l.)
   A class of Arthropoda, allied to the Crustacea. It includes
   the trilobites, Eurypteroidea, and Limuloidea. All are
   extinct except the horseshoe crabs of the last group. See
   {Limulus}.

Source : WordNet®

Merostomata
     n : used in some classifications; includes the orders Xiphosura
         and Eurypterida [syn: {class Merostomata}]