136 



ZOOLOGY. 



similis, lives in brackish water, according to Claus. Sup- 

 posed plates of Holothurians have been found in the 

 Jurassic rocks. 



Class IV.— HOLOTHUROroEA. 



'Worm-like, cylindrical Echinoderms, with a muscular body-waU tisuaUy 

 tontaining calca/)-e</iis bodies ; with a circle oflrancTied temtades, a termijud, 

 opeTiiTig of the intestine, madreporic plate internal, and usuaUy a res- 

 piratory caecal appendage. TJnisejyual or bisexual, developing by a metaTnor- 

 p!wsisfrom cylindrical, auriculated, free-s^oimming lanxB; or a/metaJ)oUrus. 



Order 1. Apoda. — No ambulacral feet. Family 1. SyruiptickBi^wpjTgas, 

 Chirodota, Synapta). Family 2. Mdpadid/B (Caudina, Mol- 

 padia). 



iyrdeir 2. Pedaia. — ^Respiratory tree present, and the ambulacral feet. 

 BisexuaL Family 1. Dendrochirotce (Thyone, Psolijs, Echi- 

 nocucumis, Pentacta). Family 2. A spidochirotcB (B.olothxi' 

 ria). Tbe Elasipoda are a group of deep-sea forms. 



Tabttlab View op the Classes and Obdebs of Echinodermata. 



Pedata. 

 (Holothnria.) 



Apoda. 

 (Chirodota.) 



HoLOTHUBOrDEA. 



Atiiechinida. 

 (Echino^.) 



Pnlichimdn. 

 (Melonltes.) 



EcHDTOroEA. 



Asteridea. 

 (Asterlas.) 



Ophinridea. 

 (Oplunra.) 



Asteroidba. 



Bradiiata. 

 (Encrinns.) 



Oystidea. 

 (Sphseronites.) 



Blaxtoidea. 

 CPentremitei.) 



Crinoidea. 



I 



ECHINODERMATA. 



