LIFE OF THE PLEISTOCENE 



Pisidium kirklandi 



" noveboracense 



" pauperculum 



" politum 



" politum decorum 



" sargenti 



" splendiduhtm 



" variabile 



" virginiatm 



Amia calva 

 Lepomis species 



Pisces 



Planorbis trivolvis 

 " deflectus 

 " exacuous 

 " parvus 

 Segmentina armigera 

 Galba obrussa 

 " palustris 

 " reflexa 

 Lymnaea stagnalis appressa 



Silurid or Cyprinoid 



The fish are represented by portions of skulls, scales, and isolated bones. 

 In the case of Amia, however, a single rather complete skeleton was found. 



It will be observed that the molluscan fauna of the bay was rich and varied, 

 consisting of species representing all of the important families of fresh water 

 shells. Compared with the preceding stage the decrease in the Unionidae is 

 notable (from 17 to 7 species) as is also the increase in gastropods (from 5 to 

 25 species). The larger number of Pisidia is also noteworthy (from 9 to 15 

 species). It is seen at once, by a comparison of this list with that of the pre- 

 ceding stage, that in the stage under consideration the majority of the species 

 are of shallow water types — Lymnaea, Planorbis, Physa, Ancylus, Anodonta, 

 Pisidium — indicating clearly a change of environment, i.e., from deeper water 

 with sandy bottom, to shallower water with muddy or silty bottom. The fish 

 remains were associated with the plant Chara, indicative of shallow water. 

 Wilmette Bay at this stage had become so shallow that the naiads could live 

 only in a small portion near the center and toward the deeper water north of 

 Foster Avenue, where the bay narrowed and opened into the larger bay south 

 of Foster Avenue and west of the Graceland bar. 



b. The Calumet-Sag Channel (Sag Outlet) 



A bed of sand and gravel in this channel (at 92nd Street) is confidently 

 believed to represent this low water stage. It is over four feet in thickness 

 and contains drift wood and dead shells such as may be seen in shallow water 

 or on a gravelly beach. A varied fauna is preserved in these gravels, as noted 

 below. 



Quadrula pustulosa 



Fusconaja undata 



Sphaerium acuminatum 

 occidentale 



Pisidium virginicum 

 " compressum 

 " splendidulum 

 " medianum 



Valvata tricarinata 



" tricarinata simplex 

 tricarinata confusa 

 " tricarinata unicarinata 

 Physa warreniana 

 Integra 

 " walkeri 

 Planorbis antrosus 



