TABLE OF CONTENTS. 



PREFACE 'g 



INTRODUCTION , 5 



TERMINOLOGY 



PART I. 



COMPARATIVE MORPHOLOGY OF ECHINI 31 



FORM OF THE TEST 31 



ORIENTATION 32 



THE PENTAMEBOUS SYSTEM AND VARIATION 35 



STRUCTURE OF THE SKELETON AND GROWTH 51 



THE AMBULACRUM OF THE CORONA 53 



THE INTERAMBULACRUM 62 



CHARACTERS OF BASICORONAL PLATES 69 



IMBRICATION OF CORONAL PLATES 73 



SPINES 77 



THE PERISTOME 79 



OCULAR AND GENITAL PLATES 86 



SPECIAL CHARACTERS OF GENITAL PLATES 185 



THE PERIPROCT 



THE ARISTOTLE'S LANTERN AND PERIGNATHIC GIRDLE 177 



PART II. 



SYSTEMATIC CLASSIFICATION OF ECHINI . 



PART III. 



PALAEOZOIC ECHINI 



GEOLOGICAL DISTRIBUTION 



SYSTEMATIC DESCRIPTIONS 



(5) 



