96 



LIFE OF THE PLEISTOCENE 



waters resulted in the formation of the broad sand terrace and dune ridges 

 north of Waukegan, near Rogers Park, and in other places. During the 

 recession of the lake a series of small bars and beaches were built up east of 

 the Englewood barrier; particularly large beaches were developed in the neigh- 

 borhood of Wolf Lake. Minor beachlets to the number of a hundred or more 

 were formed along the south shore of the lake, in Indiana. Between these 

 beachlets may now be found, particularly in the spring of the year, sloughs 

 of greater or less extent. 



The fauna of the Englewood stage, as the waters fell sought refuge in the 

 small sloughs, in the small lakes (Calumet, Wolf, George, Hyde) and in the 

 rivers. Doubtless other species have migrated northward and mixed with the 

 fauna of the last postglacial stage. The present fauna is rich and varied 

 as indicated in the table which follows: 63 



a. List of Molhisca Now Living in the Waters of /he A ncient Lake Chicago Basin 





Post- 

 Glacial 84 



Recent 





Lake 

 Micnigan 



Small 



lakes 



Rivers 



Sloughs; 

 swamps 





X 

 X 

 X 

 X 

 X 

 X 

 X 







X 

 X 

 X 

 X 

 X 

 X 

 X 

 X 





" rubiginosa 





X 





Crenodonta peruviana 





" undulata 





Quadrula pustulosa 







" lachrymosa 









Rotundaria tuberculata 









Pleurobema coccineum 









Pleurobema coccineum magnalacusiris.. 

 Elliptio gibbosus 



X 



X 











X 



X 

 X 





" gibbosus delicatus 







" crassidens 



X 









Lasmigona compressa 







X 

 X 

 X 

 X 

 X 

 X 

 X 



X 

 X 

 X 





" costata 



X 









" complanata 









Anodonta imbecilis 











" grandis 



X 

 X 





X 

 X 



X 



" grandis footiana 





X 



Anodontoides ferussacianus 







" ferussacianus subcylin- 

 draceus 







X 



X 



X 





Alasmidonta marginata 









" calceola 



X 



X 









93 Only the aquatic forms are listed. 



M These occur in the strata of glacial Lake Chicago. 



