CLASS ECHINOIDEA. 

 FIG. 30. 



O1 



As troph'ft tan a gas sis' 'm i. Basket-fish. 



The Basket-fish represents species having the five rays 

 subdivided till the number of ultimate branches is nearly 

 five thousand. 



CLASS ECHINOIDEA (ek i noid'e a). 

 ORDER CIDARIDEA (si dar Id'e a) 



The Sea-urchins differ from other Echinoderms, in 

 having the calcareous plates so firmly united with each 

 other, that all motion between them is precluded. The 

 investing shell, thus formed, is perforated with numer- 

 ous pores, through which ambulacral suckers can be 

 thrust, enabling the animal to move about. Protective 

 spines are invariably present, in some species number- 

 ing more than a thousand. 



