A treatise on zoology . AS J Fill. I. StromdJocj/slis pentanffulnris, oral , anus; 0, plates ; , covering-plates ; ), side-plates; in, interambnlacrals.(Reconstructed from Ponipockjs li^urcs.)ISllfjhtly enlarged. Fig. II. Cyxtaster gramdatus, from i)os-torior, showing oral surface in per-spective. The two left-hand raysretain the covering-plates, which arelost from the others. Lettering asin Fig. 1. (Reconstructed from Hallsligures.) X 3 diam. The [)rimitive sack form did not long i)ersist, but the follow-ing characters were, as a rule, impressed ui)on it: a sessil
A treatise on zoology . AS J Fill. I. StromdJocj/slis pentanffulnris, oral , anus; 0, plates ; , covering-plates ; ), side-plates; in, interambnlacrals.(Reconstructed from Ponipockjs li^urcs.)ISllfjhtly enlarged. Fig. II. Cyxtaster gramdatus, from i)os-torior, showing oral surface in per-spective. The two left-hand raysretain the covering-plates, which arelost from the others. Lettering asin Fig. 1. (Reconstructed from Hallsligures.) X 3 diam. The [)rimitive sack form did not long i)ersist, but the follow-ing characters were, as a rule, impressed ui)on it: a sessile habit,the consequent assumption of a circular, flattened form, the differ-entiation of the ui)per and under surfaces, the development ofmarginals or concentric frame-plates, and the tendency to increasethe food-gathering suiface l)y spiral coiling of the ambulacra ineither sinistral or dextral direction. According to the varied extentof these several modifications, the Kdrioasteroidea are divisible into3 families—Ag
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Keywords: ., bookcentury1900, bookdecade1900, bookpublishe, booksubjectzoology
