What is an extinct order of Merostomata, of which the genus Eurypterus is the type. They are found only in Paleozoic rocks. [Written also Eurypterida.] called?

eurypteroidea — An extinct order of Merostomata, of which the genus Eurypterus is the type. They are found only in Paleozoic rocks. [Written also Eurypterida.]. (Webster's 1913.)

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