113 



ZOOLOGY. 



suckers, excepting those at the end of the arms, which are 

 tentacle-like. We have already described the common star- 

 fish of our north-eastern coast, Asterias vulgaris Stimpson 

 (Fig. 74). This and the allied varieties are abundant on 

 mussel and oyster beds, being very injurious to the latter, 

 which serve them as food. The star-fish projects its capa- 

 cious stomach, turning it inside out, between the open 

 valves of the oyster, and sucks in the soft parts, in this way 

 doing much damage to the oyster-beds of the southern coast 

 of New England. 





Fig. 74.— Astmaa vulgaris, natural size.— After A. Agassiz. 



The bodies of star-fishes as well as sea-urchins (Echini) 

 are covered witli pedicenaria, which in the former are situ- 

 ated around the base of the spines on the upper side of the 

 body. They are pincer-like, consisting of but two prongs. 

 In the sea-urchins they are three-pronged, and scattered ir- 

 regularly over the surface of the body. Their use is not 

 really known. 



The development of this species (and its ally or variety, 

 A. lerylinus) has been studied by A. Agassiz. After pass- 



