218 



ZOOLOGY. 



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

 posed plates of Holothurians have been found in the 

 Jurassic rocks. 



CLASS IV. HOLOTHUROIDEA. 



Worm-like, cylindrical Echinodeiims, with a muscular body-ioaU usually 

 containing calcareous bodies ; with a circle of branched tentacles, a terminal 

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

 piratory c&cal appendage. Unisexual or bisexual, developing by a metamor- 

 phosis from cylindrical, auriculated, free-swimming larvae; or ametabolous. 

 Order 1. Apoda. No ambulacral feet. Family 1. itynaptidce (Eupyrgus, 

 Chirodota, Synapta). Family 2. Molpadidce (Caudina, Mol- 

 padia). 



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

 Bisexual. Family 1. Dendrochirotce (Thyone, Psolus, Echi- 

 nocucumis, Pentacta). Family 2. Aspidochirotm (Holothu- 

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



TABULAR VIEW OP THE CLASSES AND ORDERS OF ECHINODERMATA. 



Pedata. 

 (Holothuria.) 



Apoda. 

 (Chirodota.) 



HOLOTHUROIDEA. 



Autechinida. 

 (Echinus.) 



Palechinida. 

 (Melonites.) 



ECHINOIDEA. 



Asteridea. 

 (Asterias.) 



ASTEROIDEA. 



Brachiata. 



(Encrinus.) 



Cystidea. 

 (Sphaeronites.) 



(Pentremite*.) 

 I 



CRINOIDEA. 

 I 



ECHINODERMATA. 



