654 



THE INVERTEBRATA 



Class CRINOIDEA 



Echinodermata with branched arms; the oral surface directed up- 

 wards; attachment during the whole or part of their life by a stalk 

 which springs from the aboral apex; suckerless tube feet; and open 

 ambulacral grooves; and without madreporite; or spines; or pedi- 

 cellariae. 



The majority of the members of this class are extinct, and of those 

 that survive the typical, stalked forms (Fig. 461) live in deep water 



Fig. 458. Antedon bifida in oral view. From Sedgwick, after Claus. 



A. anus; M. mouth. 



and are less familiar than the shallow water feather stars {Antedon 

 and Actinometra) which, when they are adult, break off from their 

 stalks and swim by waving their arms. It will therefore be convenient 

 to choose one of the latter to illustrate the anatomy of the group. 

 Antedon rosacea^ the common feather star, may be dredged in ten 

 fathoms of water off the coast of England. Its body is composed of a 

 small central region or calyx and five pairs of long, slender arms^ each 

 bearing a double row of alternate branchlets known as pinfiules. On 



