THE STARFISH AND ITS ALLIES 199 



animals live in crevices of the rock, and being of rather 

 small size, are not commonly seen. At the base of the arms, 

 on the right and left, are a pair of slits, which form the 

 exits from pouches into which the reproductive glands 

 open. In certain species the pouches are used for brood- 

 ing the young. The basket-fish occur in Northeastern 



FIG. 185. Strongylocentrotus, the Eastern green sea-urchin, with tube feet 

 extended. From " Standard Natural History." 



waters, from low tide to one hundred fathoms, and are 

 often brought up by fishermen, to whose lines they have a 

 habit of clinging. The branching of the arms enables the 

 animal to hold its prey, which consists of shrimp and fish. 

 The Echinoids, or sea-urchins, may be regarded as star- 

 fishes in which the arms have shortened and the disk en- 

 larged so as to fill up the interspaces, and make a solid, 



