TABLE OF CONTENTS. 



Page. 



PREFACE 9 



INTRODUCTION •. 15 



TERMINOLOGY 25 



PART I. 



COMPARATIVE MORPHOLOGY OF ECHINI 31 



Form of the Test 31 



Orientation 32 



The Pentamerous System and Variation 35 



Structure of the Skeleton and Growth 51 



The Ambulacrum of the Corona 53 



The Interambulacrum 62 



Characters op Basicoronal Plates 69 



Imbrication of Coronal Plates 73 



Spines 77 



The Peristome 79 



Ocular and Genital Plates 86 



Special Characters of Genital Plates 165 



The Periproct 173 



The Aristotle's Lantern and Perignathic Girdle 177 



PART II. 

 SYSTEMATIC CLASSIFICATION OF ECHINI . 199 



PART III. 



PALAEOZOIC ECHINI 235 



Geological Distribution 235 



Systematic Descriptions 238 



(5) 



