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Originally appearing in Volume V08, Page 881 of the 1911 Encyclopedia Britannica.
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SPATANOOIDA Cretaceous CLYPEASTROIDA 1 Tertiary Recent L--Jaws lofty jaws flat—ryduced — lost ~— abranchiate —JL—branchiate wt—lipobranchiate—' L— no sphaeridia —a' .sphaeridia endocyclic exocyclic The probable relationship of these orders is shown in the annexed table. Here the Cystocidaroida occupy an isolated position. It is, however, quite possible that Echinocystis may some day be referred to the Cidaroida, and Palaeodiscus to the Melonitoida. This would leave the Echinoid scheme remarkably simple, with the Melonitoida and Cidaroida as divergent branches from an ancestor like Bothriocidaris; but while the former branch soon decayed, the latter continues to flourish at the present day. To take the Echinoidea now living, and to divide them into Endocyclica and Exocyclica, Branchiate and Abranchiate, Gnathostomata and Atelostomata, is easy and convenient; or again to distinguish as Palechinoidea those pre-Jurassic genera which do not conform to the fixed type of twenty vertical columns found in the later Euechinoidea, is to express an interesting fact; but all such divisions obscure the true relationships, and the corresponding terms should be recognized as descriptive rather than classificatory. zoologie concrete, iii., 1878–1887i Y. (Paris, 1904) ; A. Lang, Text-Book of Comparative Anatomy, transl., part ii. (London, 1896); Ludwig and Hamann, " Echinodermen," in Bronn's Klassen and Ordnungen des Tierreichs (Leipzig, 1889), in progress; M. Neumayr, Die Stdmme des Tierreiches (Wien, 1889); P. B. and C. F. Sarasin, Uber die Anatomie der Echinothuriden and die Phylogenie der Echinodermen," Ergebnisse naturw. Forsch. auf Ceylon, Bd. i Heft 3 (Wiesbaden, 1888) ; R. Semon, " Die Homologien innerhalb des Echinodermenstammes," Morph. .Tahrb. (1889); W. P. Sladen, " Homologies of the Primary Larval Plates in the Test of Brachiate Echinoderms," Quart. Journ. Micr. Sci., 1884; K. A. v. Zittel, Handbuch der . . . Palfiozoologie, i. pp. 308-560 (Munchen, 1879); also Grundsuge, translated and revised by C. R. Eastman as Text- 007MR!OCIDAROIDA (jaws *Anson) MELONITOIDA CYSTO• CIDAROIDA1 CIDAROIDA Permian Trias Jurassic
End of Article: SPATANOOIDA

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