The Collaborative International Dictionary of English v.0.48:

Ophiurioidea \O`phi*u`ri*oi"de*a\, Ophiuroidea
\O`phi*u*roi"de*a\, n. pl. [NL., fr. Gr. 'o`fis serpent + 'oyra`
   tail + e'i^dos form.] (Zool.)
   A class of star-shaped echinoderms having a disklike body,
   with slender, articulated arms, which are not grooved beneath
   and are often very fragile; -- called also Ophiuroida and
   Ophiuridea. See Illust. under Brittle star.
   [1913 Webster]