CONTENTS 



Page. 



Letter of transmittal 9 



Preface 11 



Introduction 13 



History and definition of the Colorado formation 13 



Geologic description 20 



The eastern border 20 



The Upper Missouri region 23 



Colorado and New Mexico 25 



Utah 34 



The relations of the Colorado fauna to other Cretaceous faunas 47 



Description of species 52 



Echinodermata 52 



Vermes 53 



Mollusca 54 



Pelecypoda 54 



Gastropoda ' 127 



Cephalopoda 163 



Arthropoda 189 



Crustacea 189 



Plates 191 



Index 283 



5 



