THE ECHINODERMATA 129 



because the arms break off easily, sometimes at 

 the will of the animal. Several kinds of them 

 are common on our shores, although they are not 

 so common as the ordinary Starfishes. Fig. 37 

 shows the general form of a Brittle Star. 



FIG. 37. A Brittle-Star, Ophiopteris antipodum. 



The Sea-Cucumbers, Holothuroidea, are an- 

 other group of Echinodermata that are repre- 

 sented on our own coasts; by small specimens, 

 however, while the Pacific Ocean furnishes in- 

 stances of larger size the Trepangs which are 

 used by the Chinese as articles of food. The 

 name Sea-Cucumber is given in fanciful compari- 



