THE STARFISH AND ITS ALLIES 



197 



rias vulgaris belongs to the gionpAsteroidea. 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. 



t ,-, , . . A Reduced. From Leunis. 



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- 

 fish, about 10 centi- 

 metres in d i a m e t e r, 



called Oribrella 4 san- 



1 APT-TIP, star ; eTSos, form. 



2 o>x/>6s, pale yellow. 



3 giyanteus, 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, 



