64 



LIFE OF THE PLEISTOCENE 



and referred to nine genera. Some years ago a number of these shells were 

 submitted to the writer and the following species were observed. 



Galba palustris 

 " reflexa 

 " caper ata 



Planorbis trivolvis 



Physa warreniana 

 Ancylns species (broken) 

 Goniobasis livescens 

 Pleurocera elevatum 



A search recently made by Dr. Grant failed to disclose the shells from the 

 Evanston deposit, in the museum of the Northwestern University, and it is 

 probable that they were packed away by Dr. Marcy and have escaped observa- 

 tion. The Unios cannot, therefore, be identified. In stratum VII of Grant's 

 section the following species were noted. 



Atnnicola lustrica Planorbis trivolvis 



Planorbis parvus 



No plants have been specifically identified from the carbonaceous strata 

 of the 1912 section. In Marcy's section, however, plants and other life were 

 identified as noted below. 



Strata 



Marcy's No. 



Plate IV, I 



Deposit 



Species 



Stratum 

 it 



5 

 6 

 9 



6 



5 

 A 



Gravel 



Sand 



Humus 



Odocoileus virginianus (femur) 

 Quercus marcyana (wood) 

 Picea evanstoni (wood) 



The Quercus has not been rediscovered in any of the recent deposits studied. 



V. Previous Glaciations in the Chicago Area 



It is believed that at least one interglacial interval, preceded by an extensive 

 glaciation, is represented in the glacial deposits of the Chicago Area. Leverett 10 

 gives evidence showing the presence of a preglacial valley beneath the drift, 

 which entered the great valley now occupied by Lake Michigan near Lincoln 

 Park. This small valley may be traced westward for several miles, the depth 

 to rock being from 115 to 125 feet. 



Old soil zones have been observed in many wells in and about the Chicago 

 region. In the northwestern part of Cook County a black soil is penetrated 

 at a depth of over 100 feet. At Arlington Heights a black soil was observed 

 at a depth of 70-75 feet. A well section in township 41, range 10 east, gave the 

 following log: 



Yellow till 10-15 feet 



Blue till 125 " 



Black soil 4 " 



la Illinois Glacial Lobe, pp. 583-587. 



