40 ANNALS NEW YORK ACADEMY OF SCIENCES 



Page 

 Paleontology 126 



Flora of the Morrison formation 126 



Invertebrate fauna of the Morrison formation 126 



Pelecypoda 126 



Gastropoda 129 



Ostracoda 130 



Arundel forms 130 



Vertebrate fauna of the Morrison formation 131 



Mammalia 131 



Aves 134 



Reptilia 134 



Dinosauria 134 



Sauropoda 134 



Theropoda 140 



Predentata 143 



Rhynchocephalia 148 



Orocodilia 148 



Ohelonia 149 



Pterosauria 149 



Pisces = . 149 



Age of the Morrison formation 150 



Origin and interpretation of the Morrison formation 157 



Summary of characters 157 



History of previous opinions as to the origin of the formation 161 



Discussion of previous theories of the origin of the formation 163 



Preliminary statement of present interpretation ■ 164 



Characteristics of recent alluvial plains 165 



Color of sediments 167 



Interpretation of the origin of the Morrison formation 169 



Bibliography 172 



INTRODUCTION 

 Peeliminart Remakks 



The present paper is the result of a study of the Morrison formation 

 undertaken by the writer in connection with the monograph on the Sauro- 

 poda now in course of preparation for the United States Geological Survey 

 by Professor Henry Fairfield Osborn. Library and laboratory work was 

 done during the winters of 1912-1913, 1913-1914 and 1914-1915 at the 

 American Museum of Natural History and at Columbia University. 

 Field work was done in the summers of 1913 and 1914. The writer 

 desires to express his thanks to Professor Osborn for the opportunity of 

 studying the Morrison formation in the field, and for permission to use 



