136 



ZOOLOGY. 



sitnilis, lives in brackish v/ater, according to Clans. Sup- 

 posed plates of Holothurians have been found in the 

 Jurassic rocks. 



Class IV.— HOLOTHUROIDEA. 



Wonn-liks, cylindriccd EchinofUrms, wUh a muscular body-wnU usually 

 containing calcareous bodies ; with a circle ofbranclied tentadss, a terminal 

 opening of the intestine, madreporie plate internal, and usually a res- 

 piratory ccecal appendage. Unisexual or bisexual, developing by a metamor- 

 phosis from cylindrical, auncvlatml, free-swimming larvm; or ametabolons. 

 OrcUrl. Apoda. — No ambulacral feet. Family 1. (%)ia;?fo'(to(Eiipyrgus, 



Cliirodota, Syuapta). Family 2. MolpadidcB (Caudina, Mol- 



padia). 

 Order 2. Pedata. — Respiratory tree present, and the ambulacral feet. 



Bisexual. Family 1. Bendrochirotm {Thyone, Psolus, Eehi- 



nocucumis, Pentacta). Family 2. Aspidochirotce (Stichopus, 



Holothuria, Aspidochir). 



Tabulae View op the CLASSEa and Obders of Echinodbbmata. 



Pedata. 

 (Holothuria.) 



Apoda. 

 (Chirodota.) 



HOLOTHUBOIDBA. 



Antechinida. 

 (Echinus.) 



Palechinida. 

 (Melonites.) 



EOHINOIDBA. 



Asteridea. 

 (Apterias.) 



Ophinridea. 

 (Ophiura.) 



ASTBROIDBA. 



Brachiata. 



(Encrinus.) 



Cystidea. 

 (Sphseronites.) 



Blastmdea. 

 (Pentremites.) 



I 



Crinoidea. 



ECHINODERMATA. 



