THE LIFE OF GLACIAL LAKE CHICAGO 



89 



Pisidium fallax Planorbis campamdalus 



Campeloma integrum obesum deflectus 



Goniobasis litesccns depygis " parvus 



Amnkola limosa Segmentina armigera 



" lustrka Galba obrussa exigua 



" obrussa dec am pi 



" palustris 



". vjoodruffi 



c. The Desplaines Valley 



In the Valley of the Desplaines River near Lemont a bed of silt and marl 

 overlies the Niagara limestone, which contains molluscan species similar to 

 those in the Wilmette Bay deposits. The location of this deposit is near the 

 595 foot contour and the mollusks evidently lived along the edge of the old 

 outlet in shallow water, out of reach of any strong currents. The level of the 

 lake at this time was probably too low to allow of much of a discharge thru 

 the Chicago outlet and the valley may have been simply a long narrow bay 

 during this low water period. The water was evidently loaded with fine sedi- 

 ment, a deposit nearer the center of the valley, which is believed to be correla- 

 tive with this episode, being 58 inches in thickness. The life of the strata at 

 Lemont is as noted below. 



Pisidium compressum 

 " mainense 

 " splendidulum 



Valvata tricatinata 



Amnkola limosa 

 " lustrka 



Goniobasis livescens 



Campeloma integrum 



Physa warreniana 

 " iniegra 



Segmentina armigera 



Planorbis antrosus 



" campanulatus 



" trivolvis 



" deflectus 



" exactions 



" parvus 

 Galba reflexa 

 " obrussa 

 Lymnaea stagnalis appressa 

 Succinea avara 



A peat bed above the silt deposit, contains biotic remains indicating a still 

 greater shallowing of the water, perhaps preceding a temporary land surface. 

 The fauna of this bed includes: 



Valiala trkarinala 

 Amnkola limosa 

 " lustrka 

 Physa gyrina 

 Planorbis exacuous 

 Segmentina armigera 



Mollusca 



Planorbis parvus 

 " trivolvis 

 Galba obrussa 



" obrussa decampi 



" reflexa 

 Lymnaea stagnalis appressa 



Vertebrates 



Odocoileus virginianus. Skull 

 Fiber zibelhkus. Skull 



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