ECHINODERMA TA. 



255 



are found at moderate depths, but there are some species which are 

 found at the great depth of 1,250 fathoms. 



Star-fishes are met with in almost every sea and under all latitudes, 

 but they are most numerous and their forms are more richly varied in 

 the seas of tropical regions. 



tig. 104. — Aitenas rubens (Lamarck;. 



The body ot the Asterias is supported by a calcareous envelope 

 composed of juxta-imposed pieces at once various and numerous. 

 The number of these pieces is estimated at more than 11,000 

 in the Red Sea Star-fish {Asterias rubens, Fig. 104), a species 

 very common in Europe. The body of the Asterias rubens is 

 likewise furnished with spines, granules, and tubercles, the shape, 

 number, and disposition of which serve in many cases to characteriere 

 the genera and the species. 



