INDEX TO THE STRATIGRAPHY OF NORTH AMERICA. 



By Bailey Willis. 



Chapter I. 

 INTRODUCTION. 



CONTENTS. 



The "Index to the stratigraphy of North America" is a compilation designed 

 to explain the geologic map which accompanies it. The compiler has assembled 

 the latest or most authoritative statements of fact and opinion, selected according 

 to his best judgment. He has been most helpfully advised by many colleagues, to 

 whom he is under more obligation than he can here express. In a subjoined list 

 (pp. 30-61) scientific credit is given to each person who has taken part in the work 

 or from whom contributions have been received. 



The material selected comprises discussions of stratigraphy, some citations of 

 fossUs, and some views on correlation. The aim has been to state stratigraphic 

 facts as fully as the data available or the scope of the woi'k permit and to include 

 as much as space allows relating to faunas and correlation. Quotation is preferred, 

 but where it was not practicable an abstract of facts has been made and the 

 reference given. 



The sources from which quotations have been taken include publications of aU 

 kinds, official, serial, and occasional. They are listed in the bibliography on pages 

 840-865. Many more have been consulted. The entries in the bibliography are 

 numbered consecutively and corresponding numbers, printed as "superiors," are 

 used in the text to indicate references. 



The method of procedure in selecting material was based on the map, which 

 furnishes the information that strata of a given age occur in a certain locality. If 

 no other clue was available the province or State was looked up in the indexes to the 

 volumes of the "Bibliography of North American geology," ^'^' ^''- ^'°' ""'' ''^- ^"^ 

 where the latest writing, at least since 1892, may be traced to the authors. In case 

 a specific formation was in question, its name was followed up in the same indices 

 or lists and all references to it during the last 18 years considered. In the later 

 works earlier ones are usually cited. Occasionally some one geologist is so identified 

 with the investigation of a particular subject or region that immediate reference to 

 his works was suggested, but not in any instance intentionally to the exclusion of 

 other observers. 



