A treatise on zoology . arm-plate. surrounded by three circlets, each of five plates ; these were onceregarded as homologous with plates in Asteroids and Ciinoids, andtherefore named the infra-basals, basals, and radials. In somespecies,such as Ophiomitra exigua, the two circlets of radially situated plates are absent, and only thecentral and basal plates arepresent. In Ophiocrenc andOphiura convcxa, Lym. sp., thereare only the central plate andthe radials; in Ophiura minufa,Lym. sp., there are the central,radial, a!id basal plates. Thelast j)ossible combination occursin a species of Pectinura
A treatise on zoology . arm-plate. surrounded by three circlets, each of five plates ; these were onceregarded as homologous with plates in Asteroids and Ciinoids, andtherefore named the infra-basals, basals, and radials. In somespecies,such as Ophiomitra exigua, the two circlets of radially situated plates are absent, and only thecentral and basal plates arepresent. In Ophiocrenc andOphiura convcxa, Lym. sp., thereare only the central plate andthe radials; in Ophiura minufa,Lym. sp., there are the central,radial, a!id basal plates. Thelast j)ossible combination occursin a species of Pectinura (), in which the two circlesof plates round the central havebeen described as the ratlialsand infia-basals. In some otherforms, such as OpJiioceramis oh-strida, Iaux. (Fig. XXHI.), thereis a remarkable uniformity in theplates on the dorsal aspect, butthese aie not arranged on thecalicular plan. In sonie otlier cases, such as Ophiura inornaia, (Fig. XXIV.), there are two infia-basal plates side by side. Fid. )or«al plates of Jfdhiurn, sp. (Aftrr llcll.) THE 26y below cjich nuliiil. The genus in which these supposed calycinalphites most reseml)le ii Crinoid cup is the genus Ophiopijrgus
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Keywords: ., bookcentury1900, bookdecade1900, bookpublishe, booksubjectzoology
