TABLE OF CONTENTS. 



Page 



Preface v 



Systematic list of species is 



CORBICULAD^ 1 



COKBICULA 2 



Recent species 3 



Fossil species 3 



Batissa 9 



Velorita 10 



Cykena 12 



Cjrena 12 



Anomalous species .27 



SPH^ailPM . . . • ^'-' 



Recent species 33 



Fossil species ^8 



PisipiuM ^" 



Recent species 61 



Fossil species '3 



Appendix . . . • • • • » • • • • '5 



Alphabetical index "^7 



(yii) 



