THE LIFE OF GLACIAL LAKE CHICAGO 79 



and the leaves of frail water plants being perfectly preserved. Even in the 

 Toleston beach fossils are uncommon, tho they are abundant in the silts 

 formed in protected localities during this stage. 



b. Supposed Evidences of Marine Life 



Alden 32 has reported the finding of certain marine mollusks and corals in 

 the Calumet beach, near Chicago Lawn. These have been personally 

 examined, as has also much additional material from other localities. Later 

 investigation has shown this material to have been artificially introduced by 

 the American Indians, and the localities at Chicago Lawn and Palos Springs 

 may be safely cataloged as old camp sites. At Palos Springs, Mr. A. Scharf, 

 an enthusiastic archaeologist, discovered a deposit of marine shells 33 mixed 

 with flint chips. These were in the Glenwood beach, and, therefore, if the 

 arguments advanced for the presence of marine conditions during the Calumet 

 stage are used, the presence of these marine shells would lead to the hypothesis 

 of a Glenwood sea separated by a low water stage of fresh water! Similar 

 material has been found in other localities and the fact of their recent inclusion 

 in these deposits thru man's agency cannot be questioned. 



The presence of certain marine crustaceans in the Great Lakes 34 has sug- 

 gested the possible occupancy of the lake basins by marine waters. These 

 organisms, however, easily accustom themselves to fresh water and it is quite 

 probable, if not certain, that they entered the lakes by way of the North Bay 

 outlet, via the Ottawa river, during the Champlain submergence. The low 

 temperature of the glacial waters would enable these creatures to become 

 gradually accustomed to fresh water. 35 



D. THE TOLESTON STAGE 



After a period, the duration of which is not known, the lake fell fifteen 

 feet and built up a third set of shore lines from 20 to 25 feet above the present 



32 Geography of Chicago pp. 43-46; also Chicago Folio. See this volume page 14 for a 

 discussion of this subject 



33 Found 300 feet west of the post office. 



M In Lake Superior In Lake Michigan 



M ysis relicta Mysis relicta 



Pontoporeia hoyi Pontoporeia hoyi 



In Lake Onatrio " filscornis 



Pontoporeia affinis Triglopsis thompsoni 



" stimpsoni 

 36 Smith, S. I., The Crustacea of the Fresh Waters of the United States. Rep. U. S. 

 Fish Com., 1872-3, pp. 642-645, 1874. 



Nicholson, A. Bull. Geol. Soc. Amer., X, p. 1 70. 



Stimpson, W. On the Deep-water Fauna of Lake Michigan. Amer. Nat., IV, pp. 403- 

 405, 1870. 



