OBINOIDS. 
41 
Classes of Echinodekmata. 
1. Body mounted on a stalk Cnnoidea. 
2. Body with five arms; free Asteroidea. 
3. Body spherical, with long spines Echinoidea. 
4. Body elongated; skin soft, hardened hymmniQ ^\vitQ^.Holothuroidea, 
The existing Crinoids live in very deep water. Penta- 
crinus caput-medusce (Fig. 40) lives attached to rocks in 
the West Indies; others live in the Atlantic Ocean> some- 
times at the greafc depth of nearly three miles. A free 
Crinoid {Antedon, Fig. 41) lives in rather shallow water, 
