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]