82 



LIFE OF THE PLEISTOCENE 



c. Life of the Toleston Stage 

 i. Wilmette Bay 



During the Toleston stage (or possibly the latter part of the Calumet stage) 

 a rich naiad fauna took possession of the deeper portion of the bay. . These 

 are of the heavy Mississippi River type of mussels; these animals usually live 

 in water from 5 to 20 feet in depth, which fact accounts for their absence in 

 the strata north of Devon Avenue, where the water was comparatively shallow. 

 As this fauna lies directly upon the Calumet gravels, it is apparent that they 

 appeared early in this stage. These mollusks were probably brot up by way 

 of the Desplaines outlet (in the glochidium stage) thru the agency of fish. 

 That the fauna was a rich one is attested not only by the number of species 

 represented, but notably by the large number of individuals, the beds in many 

 places being as thick as those now found in the Mississippi River in certain 

 favorable spots. 



The molluscan fauna of this stage is listed below: 



Fusconaja undata 

 Crenodonta undulata 



" peruviana 

 Quadrula pustulosa 



" lachrymosa 

 Rotundaria tuberadata 

 Pleurobema coccineum magnalacuslris 

 Elliptic* crassidens 



" gibbosus 

 Lasmigona costata 

 Obliquaria reflexa 

 Amygdalonajas elegans 

 Proptera alata 

 Eurynia ellipsiformis 



" recta 

 Lampsilis luteola 



" ventricosa 



Sphaerium rhomboideum 

 " sulcatum 

 " flavum 

 " strialinum 



Pisidium compressum 

 " scutellatum 

 " virginicum 

 " variabile 

 " affine 

 " walkeri 

 " politum 

 " splendidulum 

 " pauperculum 



Campeloma integrum 

 " subsolidum 



Goniobasis livescens 



Amnicola limosa 

 " letsoni 



35 species are represented of which 30 are bivalves. Three of the species 

 are especially notable. Unio (Elliptio) crassidens does not now live in this 

 region, its nearest records being Utica, La Salle County, 80 miles southwest 

 and Carroll County, 125 miles west of Chicago. That this species attained a 

 more northern range during the Toleston (or an earlier) stage s evidenced by 

 the discovery of a specimen some years ago, by Mr. George Wagner, 36 in deposits 

 near Green Bay, Wisconsin. In view of the northern extension of the fossil 

 form, it may be of interest to tabulate the northern limit of the distribution 

 of the recent form, and to compare it with the Green Bay fossil record. 37 



36 Nautilus, XVIII, pp. 97-100, 1905. 



37 These records are taken from recent reports. 



