THE LIFE OF GLACIAL LAKE CHICAGO 81 



south of Central Avenue. North of Devon Avenue the depth did not exceed 

 7 feet. It is conceivable that the points and spits of the shores developed 

 hooks of greater or less size, which fluctuated with the violence of the waves. 

 This ancient bay may be compared with Braddock's Bay, New York, which is 

 a small body of water on the south shore of Lake Ontario, near Rochester. 

 Braddock's Bay has a length of over a mile and a width of half to three quarters 

 of a mile. Its depth does not exceed 9 feet, and in most places it is less than 

 5 feet in depth (Plate XXXLX). 



A large portion of the basin in which Braddock's bay lies (especially the 

 southern portion) is a vast marsh in which the water is from 6 to 18 inches in 

 depth, and which is covered with such plants as Typha latifolia, Sparganium 

 eurycarpitm, Sagittaria latifolia, Pontederia cordata, and Decodon verticillatus. 

 The water is more or less filled with such aquatic plants as Ckara, Lemna, 

 Potamogeton, Scirpus, Nymphcea advena and Castalia odorata. Several years 

 ago careful measurements were made the length and width of the bay which 

 indicate that the embayment is gradually filling up. Sand is rapidly being 

 driven in by the waves, the two long sandy points at either end of the shore 

 attesting the violence of this agency (Plates XL, XLI). The hooks are gradual- 

 ly extending and will eventually enclose all but a very small portion of the bay. 

 The fauna is large and varied including sand-loving and swamp-loving animals. 



b. Mollusk Fauna of Braddock's Bay 



Elliptio complanalus Amnicola emarginata 

 Anodonta marginata " limosa 



" grandis " lustrica 



" grandis benedictensis Physa gyrina 

 Lampsilis nasata " ancillaria 



" radiata Ancylus parallelus 



luteola Segmentina armigera 



" luteola rosacea Planorbis parvus 

 Sphaerium sulcatum " hirsutus 



" fabale " antrosus 



Campcloma decision " campanulatus 



" integrum " trivolvis 



Valvata obtusa (introduced) Galba humilis modicella 

 " tricarinata " obrussa 



" bicarinata perdepressa " palustris 



Somatogyrus subglobosus " catascopium 



Bythinia tentaculala Pseudosuccinea columella 



Lymnaea stagnalis appressa 



It is of interest to compare this fauna with that of the ancient Wilmette 

 Bay, which was doubtless physiographically similar, the difference being in 

 the preponderance of the naiades in the latter deposit. During a late stage of 

 Lake Iroquois, Braddock's Bay was a much larger body of water, comparable 

 in both extent and depth with Wilmette Bay. 



