MONOGRAPH OF THE EXISTING CRINOIDS. 165 



Tlius in the asteroids we know that the terminals at the end of the arms are reaU}- 

 body plates pushed outward by the growth of the amas and by the addition of now 

 plates just beneath them. And similarly we are equally sure that in the echinoids 



FiQ. 103.— Latebal view of a specimen of Antedon petasus from Sweden, sHowraa the eelath-e propobtions of the 



ABM9, PDJNDLES, CENTEODOESAL AND aBRI. 



the primitive position of the coronal ring is around the mouth, it having been shoved 

 to a position about the poriproct by the entire growth of the body ha^^ng been 

 ventralward, jtost as it is outward in the asteroid arm, forming new plates as it 

 goes. 



