ASTEKIOIDEA. 

 FIG. 680. 



449 



Key-liole-Urclim, Meilila quinquefora, Agassiz. 

 Tropical America. 



SUB-SECTION IV. 

 THE ORDER OF ASTERIOIDEA OR STAR-FISHES. 



THE Star-fishes are echinoderms which are more or less 

 star-shaped, the disk or central portion gradually merging 

 into the rays. Beneath each ray there is a large number 

 of locomotive suckers, like those of the sea-urchins 

 already described. The mouth is on the under side in 

 the center, and there is an eye, or eye-spot, at the end of 

 each ray. 



By means of the ambulacral tubes, or suckers, Star- 

 fishes move over the rocks and all kinds of surfaces ; and 

 they cling to the rocks so firmly that they are removed 

 with difficulty, and will sometimes even allow their am- 

 bulacra to be pulled off rather than let go their hold. 



Their covering is not solid as in the Sea-urchins, but is 



d7 



composed of movable plates, so that these animals are 



