The Collaborative International Dictionary of English v.0.48:

Echiuroidea \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.] (Zo["o]l.)
   A division of Annelida which includes the genus Echiurus
   and allies. They are often classed among the Gephyrea, and
   called the armed Gephyreans.
   [1913 Webster]