90 LIFE OF THE PLEISTOCENE 



d. Windsor Park, South Chicago 



At the corner of 75th Street and Jeffrey Avenue a deposit of sand and gravel 

 occurs, five feet below the surface, which contains fourteen species of mollusks, 

 as noted below. 



Sphaerium striatinum Valvata bicarinata perdepressa 



Pisidium virginicum Goniobasis livescens 



" compressum confertum? Amnicola lustrica 



" superius " emarginata 



" mainense (related to, but distinct) " letsoni 

 Galba catascopium Somato gyrus integer 



The bedrock (limestone) outcrops nearby on Kingston Avenue, and is 585 

 feet above sea level or 5 feet above Lake Michigan. The shells were evidently 

 washed behind this rock barrier during the low water stage. The presence of 

 Amnicola letsoni is noteworthy. 



e. Evanston 



In Marcy's section of the Toleston beach, in the ridge which crosses the 

 University campus, a number of shells were found in peat and silt deposits, 

 beneath heavy beds of beach sand and gravel believed to be of Hammond age. 

 From this, and from an equivalent deposit in a section more recently studied 

 by the writer fourteen species have been identified. 



Sphaerium sulcatum Ancylus species 



Pisidium dubium ( = virginicum). Planorbis trivolvis 

 Goniobasis hvescens " campanulatus 



Pleutocera elevatum " parvus 



Amnicola limosa Galba palustris 



" lustrica " reflexa 



Pkysa warreniana " caperata 



Naiad shells were observed but too much decomposed to permit of identi- 

 fication. Anodonta grandis footiana was probably represented. An oak, 

 named Quercus marcyana by Prof. Penhallow, was obtained in considerable 

 quantity from the sand deposit above the peat bed (see 4 and 5 in I of Plate 



IV). 



F. THE HAMMOND STAGE 58 



Differential uplift in the region of the Trent Valley eventually raised the 

 height of the Kirkfield outlet until the waters again discharged thru the Chicago 



68 In a previous paper (Baker, Trans. 111. Acad. Sci., TV, pp. 109-116) the two last stages 

 of the postglacial lake were designated "Middle Toleston "and "Lower Toleston. " Strati- 

 graphically this produces a geological absurdity, Lower Toleston being placed above Upper 

 Toleston. These terms are correct for the lake stages but are not correct for geological strata. 

 For this reason the term Hammond is here substituted for Middle Toleston and Englewood 

 for Lower Toleston, these names being quite as appropriate as the terms Glenwood, Calumet, 

 and Toleston. 



