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-icall ujuatty 

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

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

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

 phosis from cylindrical, auriculated, free-sioimming larva; or ametabolous. 



Order 1. Apoda. No ambulacra! f eet. Family 1. tfynaptidce (Eupyrgus, 

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

 padia). 



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

 Bisexual. Family 1. Dendrochirotce (Thy one, Psolus, Echi- 

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

 Holothuria, Aspidochir). 



TABULAR VIEW OF THE CLASSES AND ORDERS OF ECHINODEKMATA. 



Pedata. 

 (Holothuria.) 



Apoda. 

 (Chirodota.) 



HOLOTHUROIDEA. 



Autechinida. 

 (Echinus.) 



Palechinid.a. 

 (Melonites.) 



I 



ECHINOIDEA. 



Asteridea. 

 (Asterias.) 



Ophiuridea. 

 (Ophiura.) 



ASTEROIDEA. 



Brachiata. 



(Encrinus.) 



Cystidea. 

 (Sphaeronitee.) 



Blastoidea. 

 (Pentremites.) 



CRINOIDEA. 



ECHINODERMATA. 



