||Ech`i*u*roi"de*a (?), n. pl. [NL., fr. echiurus, the name of one genus (Gr. 'e`chis an adder + o'yra` tail) + -oid.] (Zoöl.) A division of Annelida which includes the genus Echiurus and allies. They are often classed among the Gephyrea, and called the armed Gephyreans.