THE STARFISH AND ITS ALLIES 



197 



rias vulgaris belongs to the group Asteroidea. 1 But there are 

 over five hundred other species of starfishes. In some of 

 these as in Asterias the skele- 

 tal plates of the skin make a net- 

 work ; in others they 

 form a solid calcare- 

 ous covering. To the 

 first class belong, besides 

 Asterias vulgaris, Aste- 

 rias ocliraceaf which oc- 

 curs commonly on the 

 Pacific coast from Sitka, 

 Alaska, to San Diego, 

 California. This has a 

 much thicker, more 



solid skin than the FIG. 182. Solaster, a multirayed starfish. 



Atlantic species. A. gi- 



gantea* attains a diam- 

 eter of over two feet. 

 Next to A. vulgaris, 

 our commonest Eastern 

 species is a smooth, 

 leathery, blood-red star- 

 '6p~\ fish, about 10 centi- 

 metres in diameter, 

 called Cribrella * san- 



star ; e?5oj, form. 

 , pale yellow. 



3 yiganteus, gigantic. This 

 species occurs on our Pacific 

 FIG. 183. Archiaster, a webbed starfish. coast. 

 Slightly reduced. Photo, by W.H.C-P. 4 cribrum, sieve, 



