94 LIFE OF THE PLEISTOCENE 



barrier became a bar varying in width from one-half to nearly two miles. From 

 North Avenue to Foster Avenue the bay had a length of nearly five miles and a 

 maximum width of a mile and a half. From Foster Avenue the bay extended 

 northward as a narrow bayou less than a quarter of a mile wide; near Lincoln 

 Avenue it spread out, forming two arms, and becoming a little over half a mile 

 wide. The total extension of the bay north of Foster Avenue was a trifle over 

 two miles. It varied from 4 to 12 feet in depth. The character of the deposits, 

 as well as the life contained therein, show that the bay was for the most part 

 shallow and its waters quiet. It was doubtless bordered by cat-tails, rushes, 

 and reeds, and the shallow waters are known to have contained Chara, 

 Potamogeton, and other aquatic vegetation. 



Sometime during the Englewood stage a long bar was formed which ex- 

 tended from the southern end of the Graceland bar, at the south end of Lin- 

 coln Park, to the Hammond shore line near South Englewood, passing east of 

 Englewood and thru Auburn Park (Plate XLIV). This bar completely shut 

 in the bay north of Mt. Forest island, producing a huge marsh, similar to that 

 now existing in the Sag region near Worth. 



a. Life of Wilmette Bay 



The mollusks which have been found in these deposits are suggestive of a 

 shallow-water, marsh-bordered bay, the Valvatas and Amnicolas occupying the 

 deeper parts and the small bivalves and the fresh water pulmonates living in 

 the shallower portions near the shore. Fourteen species occur in these deposits, 

 as shown below: 



Plants 

 Potamogeton and Najas were common plants judging by the abundance of their remains, 



Animals 

 Sphaerium sulcatum Pkysa Integra 



" stamineum " gyrina 



" solidulum ■ Planorbis antrosus 



Musculium transversum " campanulatus 



Pisidium compressum trivolvis 



" variabile " parvus 



Amnicola limosa Galba palustris 



" limosa porata " caper ata 



Valvata tricarinata 



The borings of crayfish were very numerous in this deposit, attesting the 

 presence of these crustaceans. 



b. The Sag Outlet 



In the Sag channel a bed of peaty clay lies between a clay and a peat deposit 

 and is believed to represent the bottom of the Sag outlet at the time of the 

 Nipissing (transition) stage. It is probable that but little water flowed thru 



