THE LIFE OF GLACTAL LAKE CHICAGO 



87 



The Toleston stage of the Chicago basin is apparently correlative with the 

 early part of Lake Algonquin when the waters of the Superior, Huron, and 

 Michigan basins had united; the low water stage occurring during the Kirkfield 

 stage of this episode. The low water period is indicated by beds of peat in the 

 upper part of Wilmette Bay and by thin beds of sand in the lower part. Near 

 Devon Avenue a bed of peat 38 inches thick occurs, interstratified with very 

 thin beds of fine sand, indicating shallowing conditions. In the Sag outlet 

 this stage is represented by several feet of fine gravel and sand, containing 

 pockets of fine gravel mixed with wood and shells. These deposits, with their 

 biotic contents, are indicated below. 



a. The North Shore Channel (Wilmette Bay) 



In the north shore channel the strata above the Unio bed consist of silt 

 or sandy silt, capped by a bed of peat. The biota is characteristic of shallow 

 water; the upper portion of this deposit is interstratified with sand indicating 

 shallowing conditions and the life in these upper strata embraces more typical 

 species of this condition than do those below. Wilmette Bay at this time 

 was probably similar to a portion of Braddock's Bay, New York, where the 

 water is from 5 to 9 feet in depth (Plate XLII). The fauna and flora of the 

 shallowing bay is listed below. 



Potamogeton species 

 Hypnum species 

 Najas species 

 Carex species 



Rohindaria tubercidata 

 Quadrula pustulosa 

 Crenodonta peruviana 

 Elliptio gibbosus 

 Anodonta grandis 



" grandis footiana 

 Lampsilis luteola 

 Sphaerium rhomboideum 



" solidulum 



" flavum 



stamineum wisconsinensis 

 acuminatum 



" strialinum 



" sulcatum 

 Musadium secure 



transversum 

 Pisidium affine 



" compression 



" compressum ksvigatum 



Plants 



Cliara species 

 Picea canadensis 



" mariana 

 Quercus species 



Animals (Mollusks) 



Pisidium scutellatum 



" walkeri 



" abditicm? 



Campeloma integrum 



" subselidum 

 Gonlobasis livescens 

 ■ Vatvala iricarinata 

 Amnicola limosa 



" limosa porata 

 " lustrica 

 " emarginata 

 Somatogyrus subglobosus 

 Physa ivarreniana 

 " integra 

 " gyrina 

 A ncylus fuscus 



" parallelus 

 Planorbis antrosus 



campanulatus 



