OPHIURIOIDEA. 451 



through minute holes which cover the whole surface of 

 the animal. 



Star-fishes often lose one or more of their arms by being 

 dashed against the rocks by the waves, or the arm is bitten 

 off by a fish. In such cases a new one sprouts otit in the 

 place of the old one ; and specimens may be found show- 

 ing such ne\v rays in all stages, from those that have just 

 begun to sprout, to those that have nearly reached their 

 full growth. 



SUB-SECTION V. 

 THE ORDER OF OPHIURIOIDEA OR SERPENT-STARS. 



THESE curious echinoderins, which hide under the sea 

 weeds and in the darkest crevices of the rocks of the sea, 

 have long tapering arms which start off abruptly from a 

 comparatively small and a well-defined disk. They thus 

 differ in a marked degree, even in external form, from 

 FlG 682 the true Star-fishes, which 



have the disk or cen- 

 tral portion comparative- 

 ly large^ and gradually 

 merging into the arms. 



The name of this or- 

 der is from ofthis, a snake, 

 and oimii a tail ; the 

 arms taper like a snake's 

 tail. The Ophiurans are 

 often called " Brittle 

 Stars," because they are 



Serpent-Star, Ophiopholis bfllis, Lyraan. i i /. M u 1 



exceedingly fragile, break- 

 ing at a very slight touch ; and they also readily break 

 themselves into pieces, probably by contraction. 



