210 ECHINODERMATA ECHINOZOA SUB-BRANCH m 



Order 2. CRYPTOZONIA. Sladen. 



Marginal plates inconspicuous and more or less rudimentary in the adult. 

 Supero-marginal plates often separated from the infer o-marginal series by inter- 

 mediate plates. Papulae distributed over the whole body. Ambulacral plates 

 crowded and narrow ; tube feet in two or four rows. 



Of the Palaeozoic representatives of this order, the genera Lepidaster, 

 Forbes (Silurian), and JRoemeraster, Stiirtz (Devonian), are related to the 

 recent genus Linckia, Nardo. The forms described by Stiirtz, Echinasterella, 

 Medusaster, and Protasteracanthion, from the Devonian of Bundenbach, are 

 regarded by their author as allied to the Echinasteridae, Asteriidae, and 

 Brisingidae respectively. 



Solaster, Forbes, is represented by a form having numerous arms in the 

 Great Oolite of England. Tropidaster, Forbes, occurs in the Middle Lias ; 

 and a solitary species of Echinaster, M. and T. (Ehopia, Gray), has been 

 described from the Neocomian. A form described by Forbes from the Red 

 Crag of England was considered by him to be specifically identical with the 

 existing Asterias rubens, Linn6. 1 



SUB-BRANCH III. Echinozoa. Leuckart. 



Armless and stemless Echinodermata, with globular, cordiform, discoidal, or 

 worm-like bodies, which are either encased in a plated test or are covered with a 

 leathery skin, in which minute, detached calcareous bodies are embedded. 



The Echinozoa are divided into two classes : Echinoidea or Sea-urchins, and 

 Holothurioidea or Sea-cucumbers. 



Class 1. ECHINOIDEA. Agassiz. Sea-Urchins. 2 



Echinozoa, with bodies encased in a solid or slightly flexible test, variable in shape 

 from spherical to flat; composed of numerous, closely placed, more or less geometrical 



1 [To Mr. W. Percy Sladen, Vice-President of the Linnean Society, and well known for his 

 numerous scientific achievements, the author and editor are under special obligations for having 

 thoroughly revised and enlarged the preceding chapter on the Asterozoa, and also for having 

 rendered valuable assistance on the Echinozoa. TEANS.] 



2 Agassiz, L., and Desor, E., Description des Echinides fossiles de la Suisse, 1839-40. Catalogue 

 Raisonne des Families, Genres, et des Especes de la Classe des Echinides (Ann. des. Sci. Nat.), 

 1846-47. d'Orbigny, A., Paleontologie franaise (Terrain cretace, vol. VI.), 1853-60. Cotteau and 

 Triger, Echinides du departement de la Sarthe, 1855-69. Desor, E., Synopsis des Echinides fossiles. 

 Paris, 1858. Wright, T., Monograph on the British fossil Echinodermata of the Oolitic Formations 

 (Palaeontograph. Soc.), 1857-80. Idem, Cretaceous Formations (Palaeont. Soc.), 1864-82. 

 Cotteau, G., Paleontologie frai^aise, vols. VII., IX., and X., 1862-79. Laube, G. C., Echinoder- 

 men des vicentischen Tertiargebietes (Denkschr. Wien. Akad. xxix.), 1868. de LorioL P., 

 Echinologie helvetique, vols. I. -III. Geneva, 1868-75. Quenstedt, F. A., Petrefactenkunde 

 Deutschlands (Bd. III., Echiniden), 1872-75. Agassiz, A., Revision of the Echini (111. Cat. 

 Museum Comp. Zool. Cambridge, No. 7), 1872-74. Reports on the Echini of the Hassler (1874), 

 Challenger (1881) and Blake (1883) Expeditions. Loven, S., Etudes sur les Echiuoidees (Svensk. 

 Veteusk. Akad. Handl., Bd. XL), 1874. Cotteau, Peron, and Gauthier, Echinides fossiles de 

 1'Algerie. Paris, 1876-91. de LorioL P., Monographic paleontologique, etc. (Abhandl. Schweiz. 

 pal. Gesellsch. III. -VIII.), 1876-81. Dames, W., Die Echiniden der vicentischen und veronischen 

 Tertiar-Ablagerungen (Palaeontographica, Bd. XXV.), 1877. Agassiz, A., Palaeontological and 

 Embryological Development (Address before Amer. Assoc. Adv. Science), 1880. Bibliography of 

 the Echinodermata (Bull. Museum Comp. Zool. Cambridge, vol. X., No. 2), 1882. Duncan, P. M., 

 and Sladen, W. P., Monograph of the fossil Echinoidea of Western Sind (Palaeont. Indica, Ser. 



