74 ECHINODERMATA. 



Class I. Crinoidea. Sea Lilies. 



Spherical, goblet- or cup-shaped ; fixed when young or permanently 

 by a jointed calcareous stalk. Possess branched arms, usually furnished 

 with pinnules. A nervous system on the aboral side of the body, in addi- 

 tion to the ordinary one. Groups of tentacles are formed by side 

 branches of the radial water-vascular vessels. No madreporic plate or 

 stone- canal, but water-tubes opening into the enterocoelic body-cavity, 

 which again communicate by water-pores with the exterior. Many fossil 

 forms ; recent examples mostly inhabitants of the deep sea. Encrinus 

 liliiformis from the Muschelkalk. Pentacrinus caput Medusse, recent. 

 Comatula (Antedon) rosacea, feather star, stalked when young, later 

 on free. 



