72 LIFE OF THE PLEISTOCENE 



Lampsilis lideola . Campeloma integrum 



Sphaerium sulcatum " integrum obesum 



" solidulum Physa warreniana 



" striatinum " gyrina 



" flavum Ancylus fuscus 



" stamineum Ancylus parallelus 



" stamineum unsconsinensis Segmentina armigera 



" acuminatum Planorbis trivolvis 



Pisidium affine " campanulatus 



" compression " antrosus 



" idalioense *■ " deflectus 



" variabile " exacuous 



Valvata tricarinata " parvus 



Goniobasis livescens Galba reflexa 



" palustris 

 Lymnaea stagnalis appressa 



The majority of the species are represented by a multitude of individuals 

 showing that life was abundant during this period. All of the species are north 

 temperate and boreal in distribution; many, indeed, extend as far north as the 

 60th and 70th degrees of north latitude. It is not remarkable, therefore, that 

 this life should have followed so closely the retreating ice. The oak, spruce 

 and other conifers are also indicative of a cold-temperate climate; the spruce 

 does not now live within about one hundred miles of Chicago, and the other 

 trees are of northern distribution. The late Prof. Penhallow 12 compared the 

 spruce found at Evanston to Picea sitchensis, a species of the west coast of 

 America. The spruce found in the north shore channel has been identified as 

 Picea canadensis, which is abundant in southern Michigan and Wisconsin, 

 and extends northward to Alaska and Hudson Bay. 



The number of specimens of the cones and the wood of the spruce, and the 

 wood and leaves of the oak, and other trees point to the abundance of these 

 species during this period. Of the spruces Prof. Davis said: "These conifer 

 remains occur in such abundance in the sandy material that it would seem 

 highly probable that the trees from which both the leaves and cones came, must 

 have been abundant in the immediate vicinity of the lake during the time when 

 the deposits were being formed. It does not seem likely that so much material 

 of this sort, unmixed with other plant remains could have been washed down 

 the shore of the lake from the north, for any distance, and at the present time, 

 Picea canadensis is found only a considerable distance to the north of your 

 locality. " 



As the strata containing these evidences of life do not extend far beyond 

 Devon Avenue, or a mile and a half north of Foster Avenue, it is apparent that 

 the level of the lake could not have been much over ten feet higher than the 

 present level. The ground moraine in this area is notably undulating, forming 



"Trans. Roy. Soc. Canada, LX, pp. 29-32, 1891. 



