CHAPTER XII. 



ECHINODERMATA. ' 



Classes. i. Holothuroidea. Sea-Cucumbers. 



2. EcHiNOiDEA. Sea-Urchins. 



3. AsTEROiDEA. Starfishes. 



4. Ophiuroidea. Brittle-stars. 



5. Crinoidea. Feather-stars. 



6. Blastoidea. Extinct. 



7. Cystoidea. Extinct. 



The Echinodermata include seven classes, of which two 

 are wholly extinct. 



Holothuroidea. 

 Sea-cucumbers. 



(Scytodermata.) 



EcHiNOiDEA. Asteroidea. Ophiuroidea. 

 Sea-urchins. Starfish. Brittle-Stars. 



(Echinozoa.) 



Crinoidea, and the extinct Blastoidea and Cystoidea. 

 Feather-Stars. 



(Pelmatozoa.) 



General Characters of Echinodermata. 



The Echinoderms are marine, and feed on organic debris, 

 or, less frequently, on living animals. 



