THE STAEFISH 



251 



Systematic Position. — The starfishes belong to the group 

 of Echinodermata/ as is proved by their five-rayed structure; 

 the well-developed system of limy plates in the skin; a system 

 of water-tubes, used for loco- 

 motion ; and the separation 

 of the intestine from the 

 body-cavity. 



Distribution and Habitat. 

 — The common pirLk star- 

 fish of the eastern United 

 States (Asterias ^ vulgaris ^) 

 ranges from Labrador to 

 northern Florida.^ It hves 

 near the shore, extending out 

 into fairly deep water, but is 

 not abundant at greater 

 depths than sixty fathoms. 

 It is found especialljr on the oyster-beds, where it is very destruc- 

 tive. On rocky coasts starfishes will be found in crevices of the 

 rock or in tide-pools. They love cool waters, and are often 

 found hanging on vertical walls or ledges. Upon reaching the 

 surface of quiet water, they may extend one or more of their 

 arms out upon the under side of the surface film and seem to 

 hang in part from it. 



Abnormalities are frequently found among starfishes, — 

 partly on account of their capacity for regeneration, even from 



Fig. 241. — Abnormal starfish (Asteriaa), 

 apparently produced by fusion of two 

 rays. One-half nat. size. Photo, by 

 W. H. C. P. 



' echinos, hedgehog, sea-urchin f derma, skin. 



' From aster, star. 



3 Common. 



^ A dark brown form, sometimes called Asterias Forhesn, is recognized by 

 some authors as a separate species inhabiting the coast from Massachusetts 

 Bay southward. 



