Echinodermata. 345 



CLASS V. THE CRINOIDEA. 



Sea Lilies. The stalked crinoids are borne on a slender 

 stalk of calcareous disks, so connected as to allow of con- 

 siderable freedom of motion. The body is flowerlike, with 



branching arms surround- 

 ing the central mouth. 

 Most of the living crinoids 

 are found in deep seas, 

 and are known 

 as the sea lilies. 

 In shallow water 

 is found a form 

 that is stalked in 

 its earlier life, but 

 later the body, 

 with its feathery 

 arms, is set free 

 and swims away by the 

 motions of the arms. These 

 are known as the feather stars. 

 Crinoids. Many fossil crinoids are 

 found in the Mississippi Valley. The 

 heads are less common, perhaps be- 

 cause, being softer, they have been 

 ground to powder. But it is common 

 to find portions of the stems, which 

 FIG. 194. A CRINOID, OR look like a series of buttons piled 

 one upon another, with a more or 

 less evident hole running through the 



center. These appear to have been so abundant in the 

 seas of former ages that they have formed whole strata of 

 limestone rock. 



