Webster’s Revised Unabridged Dictionary · 1913
Echiuroidea
Ech′i·u·roi′de·a (ĕk′ĭ·ū·roi′dē·ȧ), n. pl. [NL., fr. echiurus, the name of one genus (Gr. ἔχις an adder + οὐρά 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.