CONTENTS. 



Page 



Introduction' ....•••••■••■• "^' 



The Calyx 13 



The Arms l' 



Arm Joints 23 



Pinnules 25 



Side Plates and Covering Plates 28 



Inteeeadial Plates -j^ 



Venteal Sueface 40 



Oeals 44 



Stem 46 



The Top Stem Joint 51 



Stems of some Fossil Ceinoids ' .06 



Structure of the Stem ....... ..... 64 



The Apical System of Echinoderms 65 



On some of the Homologies of Echinoderms 84 



