. Elementary text-book of zoology, tr. and ed. by Adam Sedgwick, with the assistance of F. G. Heathcote. 294 .ECHINODERMAIA. 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 plants. The anibulacral groove is always covered by special dermal plates, and the anibulacral 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 groo
. Elementary text-book of zoology, tr. and ed. by Adam Sedgwick, with the assistance of F. G. Heathcote. 294 .ECHINODERMAIA. 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 plants. The anibulacral groove is always covered by special dermal plates, and the anibulacral 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 (Astrophyton). The anus is always wanting, as are jtedicellarias. 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, , Amphiura squamata; these do not undergo metamor- phosis. Most pass through the Pluteus larval stage, Ophiogtypha Lyra., (Ophiolepis) ciliata with larval stage Pluteus FIG. 238.»-Op1tiothrij:fragi!i8. The ends of the rays have been removed. OS, Slits of the genital pouches; K, masticatory ossicles. Faru. Ophiuridae. With simple unbranched arms, and with ventral plates to the ambulacral groove. They are divided into special genera according to the pec-uliar character of the dermal covering and of the buccal armature. Opltiotliric Mull. Tr. The back is provided with granules, hairs, or spicules. The lateral plates of the arms bear spicules. Opk. fray His 0. Fr. M tiller. Ophiura Lam. [OpTlioderma). Two pairs of genital slits in each intcrbrachial space. 0. longicauda Link., Ophiolepis Liitk., Amphiura Forb. Fam. Euryalidae. Mostly with branched arms which can be curved towards the mouth and are without plates ; the ventral groove closed with soft skill. Astroplujton rcrritcuxum- Indian Ocean. -1. arlorcscens
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