136 



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 Echinoderms, with a muscular body-mall usually 

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

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

 piratory c(Kcal appendage. Unisexual or bisexual, developing by a metamor- 

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



Order 1. Apoda. No ambulacral f eet. Family 1. Synaptidce (Enpyrgus, 

 Chirodota, Synapta). Family 2. Mdpadidae (Caudiua, Mol- 

 padia). 



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

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

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

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



TABULAR VIEW OF THE CLASSES AND ORDERS OF ECHINODEIUIATA, 



Pedata. 

 (Eolothuria.) 



Apoda. 

 (Chirodota.) 



HOLOTHUROIDEA. 



Autechinida, 



(Echinus.) 



Palechinidn, 

 (Melonites.) 



ECHINOIDEA. 



Asteridea. 

 (Asterias.) 



Ophiii r idea. 

 (Ophiura.) 



Brachiata. 

 (Encrinus.) 

 ASTEROIDEA. 



Cystidea. 

 (Sphaeronites.) 



Blastoiden. 

 (Pentreinitei.) 



CRINOIDEA. 



ECHIXODERMATA. 



