44 FRANK COLLINS BAKER 



their relation to each other. Of the two evils, splitting is certainly 

 the less. In the study of the material from these deposits this 

 fact has been kept in mind and careful comparisons have been 

 made with Recent and with other fossil species. 



MATERIAL FROM THE LOESS AND OTHER DEPOSITS 

 IN NORTHWESTERN ILLINOIS 



This material was collected by Dr. Morris M. Leighton, geolo- 

 gist in charge of Pleistocene investigations for the Illinois State 

 Geological Survey, during the summer of 1920. Dr. Leighton has 

 worked out the stratigraphy of these deposits and his papers appear 

 elsewhere. The localities and sections from which the material 

 came are indicated below, the information being contributed by 

 Dr. Leighton. The molluscan species contained in these strata 

 are listed as to species and abundance. The writer has added 

 certain notes to Dr. Leighton's data, suggested by the zoological 

 content of the strata. More specific information concerning the 

 different species will be found in a later part of this paper. 



STATION NO. I 



Locality: Bluff along Farm Creek, Tazewell County, about 7 

 miles east of Peoria, just east of the Toledo, Peoria & Western 

 Railway bridge, near the south line of SE. J, Sec. 30, T. 26 N., R. 

 3W. 



Material: From the deposit of loess underlying the Shelbyville 

 till, and overlying an older leached loesslike clay and the weathered 

 Illinoian till. 



Stratigraphic horizon: Early Peorian loess. 



MOLLUSCAN LIFE 



Helicina occulta, common. Succinea ovalis, rare, immature. 



Oreohelix iowensis, broken pieces. 



All are typical Peorian loess mollusks. This is near the type 

 locality of Leverett's Peorian interglacial stage,^ and these are the 

 first mollusks to be specifically identified from this type section. 



. ^Leverett, "The Illinois Glacial Lobe," U.S. Geol. Surv. Mon. 38 (1899), p. 187. 



