62 THE VOYAGE OF H.M.S. CHALLENGER. 



Antedon eschrichti and Antedon carinata, the ambulacral plating is reduced to small and 

 irregular spicules without definite arrangement. 



By means of these various characters, then, it is possible to subdivide the large 

 specific groups, both in Antedon and in Actinometra, and to make out a detailed 

 classification of the numerous species belonging to each genus. Except in a few cases, 

 however, it would be premature as yet to make any attempt at distinguishing the 

 structural and the adaptive characters respectively among those which we are at present 

 inclined to regard as of specific value. 



