Source : Webster's Revised Unabridged Dictionary (1913)

Echiuroidea \Ech`i*u*roi"de*a\, n. pl. [NL., fr. echiurus, the
   name of one genus (Gr. ? an adder + ? 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}.