CONTENTS. 



Page 



1 NTRODUCTION 



The Calyx 13 



The Arms . 17 



Arm Joints 23 



Pinnules L'."> 



Side Plates and Covering Plates .......... 28 



Interradial Plates ............ 32 



Ventral Surface. . 40 



Orals 44 



Stem 46 



The Tcii> Stem Joint ."il 



Stems of some Fossil Grinoids .... . .... 56 



Structure of the Stem 64 



The An. al System of E< hinoderms 65 



Ok some of the Homologies of Echinoderms ....... 84 



