262 



THE OCEAN WORLD. 



Star-fishes are exclusively and essentially beings of the sea ; they 

 are never seen in fresh water ; they dwell amongst the submarine 

 herbage, seeking for sandy coasts; they generally are found at 

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

 great depth of a hundred and fifty fathoms. 



Asterias 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. There are about a hundred and forty 

 species described. 



The body of the Asteria is supported by a calcareous envelope com- 

 posed of juxta-posed pieces at once various and numerous. The 

 number of these pieces is estimated at more than eleven thousand in 

 the Eed Sea Star-fish (Asterias rubens, Fig. 105), a species very 



Fig. 106. Asterias aurantiaca (Lamarck). 



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

 furnished with spines, granules, and tubercules, the shape, number, 



