EVIDENCE BEARING ON A POSSIBLE NORTHEASTWARD 

 EXTENSION OF MISSISSIPPIAN SEAS IN ILLINOIS 



W. W. DAVIS 



University of Chicago 



CONTENTS 



Introduction 



Location of the Bowlders 



Lithologic Character of the Bowlders 



Physical Condition of the Bowlders 



Criteria by Which the Bowlders May Be Recognized 



The Fauna of the Bowlders 



The Geographic and Geologic Relationships of the Fauna 



The Place of Origin of the Bowlders 



Conclusions 



Introduction. — For some time it has been known that fossils of 

 Mississippian age can be collected within the city limits of Chicago. 

 These Mississippian fossils, which occur in bowlders in the glacial 

 drift, were brought to notice by Mr. William Johnston, who 

 reported them to Professor Weller in 1915. The collections which 

 form the basis of the present report are in part those first secured 

 by Mr. Johnston; others have been collected by Professor Weller, 

 and still others by the writer. 



Location of the bowlders. — The drift bowlders which have afforded 

 the fossils occur in the southeastern portion of the clay-pit of the 

 Carey Brick Company, located near the northeastern corner of 

 Grand Avenue and New England Avenue, in the northwestern 

 portion of the city, between Hanson Park and Montclare, being 

 closer to the latter place. The clay-pit is excavated in a terminal 

 moraine, which belongs either to the lake border or to the Valparaiso 

 morainic system, but probably to the former. 1 The morainic 



1 Areal Geology Sheet, Chicago Folio. 



576 



