19 

 THE STARFISH 



EXTERNAL FEATURES 



One of the most familiar animals of the seashore is the common 

 starfish, Asterias riibens. It may often be found dead or dying 











Fig. 213. — Part of an aboral view of a starfish {Asterias rubens) and an enlarge- 

 ment of a small part of the surface of the same. 



g., Gills ; ped., large pedicellaria ; ped'., small pedicellaria ; sp., spine. 



upon the beach where it has been thrown up, or living in pools 

 but its principal haunts are in somewhat deeper water. For all 

 its seeming helplessness, it is an exceedingly voracious animal, 

 and is particularly destructive to shellfish, so that it is a pest in 

 oyster beds. Its body, of a colour varying from orange to purplish, 

 and darker above than below, has the shape of a star, with five 

 tapering rays, or arms, meeting in a central region known as 

 the disc. The upper side is called aboral (Fig. 213), the lower 

 oral (Fig. 214), because on it, in the middle of the disc, lies the 



mouth. The direction of each arm is known as a radius. The 



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