Ophiuroidea

Definitions

  • WordNet 3.6
    • n Ophiuroidea brittle stars and basket stars
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Webster's Revised Unabridged Dictionary
    • n. pl Ophiuroidea (Zoöl) 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.
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Century Dictionary and Cyclopedia
    • Ophiuroidea An order of echinoderms of the class Stellerida or starfishes, containing the brittle-stars, sand-stars, or ophiurans. ; They are starfishes with a more or less well-defined central disk distinct from and not passing into the arms or rays, and no anal orifice. The axis of the arms is composed of a series of calcareous ossicles called vertebræ, each of which is composed of two parts representing the ambulacral plates of ordinary starfishes, and the axis is covered with plates or with continuous integument, usually bearing spines. The ambulacral nerve, water-vessels, and neural canal are within the hollow of the arm. The water-feet or pedicles are without suckers or ampullæ, and protrude between the lateral plates of the arms. The mouth is pentagonal, and each angle is composed of five pieces. The order falls naturally into two leading divisions, according as the arms are simple or branched. These are sometimes called families, Ophiuridæ and Astrophytidæ; sometimes they are considered as suborders, when the former group is known as Ophiurida or Ophiureæ, and further subdivided into several families, of which the Ophiurida proper constitute one.
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Etymology

Webster's Revised Unabridged Dictionary
NL., fr. Gr. 'o`fis serpent + 'oyra` tail + e'i^dos form