. Elementary text-book of zoology, general part and special part: protozoa to insecta. Animals. 294 rCnrN'ODERlIATA, no diverticula of the alimentary canal. The movements of the arms are principally in the horizontal plane, and in many cases permit of a creeping locomotion amongst marine jilants. The ambulacral groove is always covered by special dermal plates, and the ambulacral feet project laterally between the spicules and plates on the upper surface (fig. 238). In a few cases the arms are branched, and can be rolled up in the direction of the mouth. In such cases the ventral groove is clo
. Elementary text-book of zoology, general part and special part: protozoa to insecta. Animals. 294 rCnrN'ODERlIATA, no diverticula of the alimentary canal. The movements of the arms are principally in the horizontal plane, and in many cases permit of a creeping locomotion amongst marine jilants. The ambulacral groove is always covered by special dermal plates, and the ambulacral feet project laterally between the spicules and plates on the upper surface (fig. 238). In a few cases the arms are branched, and can be rolled up in the direction of the mouth. In such cases the ventral groove is closed by a soft skin {Astrojohyton). The anus is always wanting, as are 'pedicellarke. The generative products pass into genital pouches (bursse), and from these directly to the exterior through inter-radial paired slits. The madreporic plate lies upon the ventral sur- face in one of the buccal plates. Some few Ophiu- rids are viviparous, , Avijihiura squamata; these do not undergo metamor- phosis. Most pass through the Pluteus larval stage, , OiMoglyplia Lym., {Opldoleiiis) ciliata with larval stage Pluteus Fig. 2Z9.»-Ophiotli>-ijrfragiIig. The ends of the rays have been removed. &S, Slits of the genital pouches; K, masticatory ossicles. Fam. Ophiuridae. With simple unbranched arms, and with ventral plates to the ambulacral groove. They are divided into special genera according to the pec-aliar character of the dermal covering and of the buccal armature. Ophiothrix Miill. Tr. The back is provided with granules, hairs, or spicules. The lateral plates of the arms bear spicules. Oiih. frafjilis 0. Fr. Miiller. OjjJitura Lam. (Oj)hio(Ierina'). Two pairs of genital slits in each interbrachial space. 0. loiujiccmda Link., OjJhivlejns Liitk., AvqMnra Forb. Fam. Euryalidae. Mostly with branched arms which can be curved towards the mouth and are without plates ; the ventral groove closed with soft skin. Astrojjhyton verrucosnm Lam., Indian Ocean. A. arhoresce
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectanimals, bookyear1892
