PLEISTOCENE MOLLUSC A FROM ILLINOIS 51 



STATION NO. 13 



Locality: Whiteside County, west line of NW. \ of SE. \, Sec. 15, 

 T. 20 N., R. 3 E., road cut on upland spur. 

 Material: Shown in the following section: 



Feet 



2. Soil and leached loess i|-3 



I. Calcareous and fossiliferous loess 6 



Stratigraphic horizon: Post-Illinoian, possibly Peorian. 



MOLLUSCAN LIFE 



Seven species of land mollusks typical of the lowan loess 

 occurred in stratum No. i, as noted: 



Vallonia gracilicosta, common. Gastrocopta armifera, common. 



Vertigo modesta, rare (previously Succinea avara, common. 



known as Pupilla blandi). Pyramidula shimekii, rare. 



Pupilla muscorum, rare. Euconulus fulvus, rare. 



DISCUSSION OF SPECIES REPRESENTED IN THE DEPOSITS 



Thirty species are represented in the material collected by Dr. 

 Leighton, three of which have not before been definitely reported 

 from Pleistocene deposits in the state, and three others have been 

 reported but rarely and from deposits not clearly defined strati- 

 graphically. These are: 



New Records Rare Records 



Gastrocopta tappaniana Vertigo modesta. 



Vallonia gracilicosta. Pyramidula shimekii. 



Galba dalli. Oreohelix iowensis. 



These collections indicate that the fauna of the loess and other 

 deposits common in Iowa also occur in Illinois, at least in the north- 

 western part, and that the deposits may be rather definitely 

 correlated with those of Iowa. 



The thirty species have the following distribution as to geologic 

 age: 



