ECONOMIC ZOOLOGY 



long flexible stem, made up of disk-like segments. They occur at all, 

 though mostly moderate, depths; many are known only as fossils, 

 their calcareous skeletons helping to form extensive limestone deposits. 

 The Asteroidea are of very considerable negative importance 

 since they are a serious menace to the shellfish industry, especially 

 to oysters. A single starfish, in captivity, is said to have eaten 20 

 clams in six days, and since along the northern coasts the starfish 

 are often extremely abundant, they sometimes are very destructive to 



FIG. 17. Serpent or brittle-star. Xi. 



oyster beds. The method of getting rid of them will be discussed 

 under the head of oyster culture. 



The Echinoidea, under the name of sea-eggs, are of some, though 

 not very great, economic importance. In the West Indies, Italy 

 and in the far east they are largely eaten, both raw and cooked, 

 especially when they are sexually mature and full of eggs, as it is the 

 eggs that are eaten. A large sea-urchin just before spawning contains 

 a very considerable quantity of roe. A decade or more ago at Barbados, 

 the centre of the sea-egg industry, the annual business was worth 

 about $20,000. 



The Holothurians are the most important, economically, of the 



