116 ILLINOIS ACADEMY OF SCIENCE. 



overlying the Middle Tolleston marl beds and also in the presence 

 of crawfish burrows. 



8. Following the low-water stage the water again rose and 

 flooded the bay to the depth of ten feet, producing an embayment 

 nearly equal in area to that of the Middle Tolleston stage. This 

 (Lower Tolleston), the last of the Lake Chicago stages, was 

 characterized by an abundant fauna consisting of swamp and 

 shallow water types. This stage must have been of considerable 

 duration as silt was deposited to a depth of over two feet. 



9. The water fell to the level of Lake Michigan and the bed 

 of Wilmette Bay became a marsh, wet during the spring and dry 

 in the fall. This condition prevailed until the region was drained 

 by man during the past century. 



My thanks are due the following gentlemen for assistance : 



Dr. Rollin Chamberlin, University of Chicago. 



Mr. C. A. Davis, Washington, D. C. 



Mr. Bryant Walker, Detroit, Michigan. 



Mr. A. S. Lewis, Superintendent, Lincoln Park. 



Dr. V. Sterki, New Philadelphia, Ohio. 



Dr. A. E. Ortman, Carnegie Museum, Pittsburgh, Pa. 



U. S. Naval Station, Illinois. 



DISCUSSION. 



In answer to a question Mr. Baker said : 



"The spruce is probably the same as Penhallow's Picea Evans- 

 toni, which may be the same as Picea Canadensis. I have not yet 

 received identifications of the other plants found in these strata. 

 I know only of the spruce, oak, Chara, and Potamogeton." 



Mr. Cowles. — "Do you know what species the oak is?" 



Mr. Baker. — "I think it is Quercus Marceyana. The question 

 at issue is the stage during which the lower marsh deposits were 

 deposited. Are they post or pre-Calumet? If post-Calumet, as 

 some geologists would have us believe, then what is the heavy 

 deposit of gravel above these marsh deposits ? I think there is no 

 escape from the conclusion that they are pre-Calumet." 



