PLEISTOCENE MOLLUSC A FROM ILLINOIS 45 



STATION NO. 2 



Locality: Road cut f mile northwest of Winslow, Stephenson 

 County, just southeast of fork in roads. 



Material: Yellow calcareous sandy loess from base of cut. 

 Stratigraphical horizon: Probably early Peorian. 



MOLLUSCAN LIFE 



Succinea vermeia, a common loess fossil, usually listed as avara. 

 STATION NOS. 3 AND II 



Locality: Stephenson County, SW. I of SW|, Sec. 28, T. 27 N., 

 R. 9 E., about I mile northeast of Pecatonica River bridge, bank 

 along roadside 12 to 15 feet high, mostly grass- and shrub-covered ; 



1 mile north and | mile east of Ridott. 



Material: Exposure at one place shows yellow, loesslike clay, 

 calcareous, about 5 feet below top. Topographically a terrace 

 resembling the silt terrace of the Pecatonica farther downstream 

 and in tributary ^ mile east. No show of bedding or lamination; 

 possibly obliterated by slumping. 



Stratigraphic horizon: Probably Wisconsin, in back water from 

 Rock River during the deposition of the Rock River Valley train. 



MOLLUSCAN LIFE 



Pomatiopsis lapidaria, very abundant. Galba obnissa, seven broken shells. 

 Helicodiscus parallelus, common. 



The writer is of the opinion that this deposit may have been 

 partly formed by wind. Two of the species are semiaquatic. 

 Pomatiopsis now lives in very small streams, usually not exceeding 



2 feet in width and a few inches in depth. Galba obrussa is semi- 

 aquatic (or amphibious) and spends as much time out of the water 

 as in it. Its habitat is in such streams as above described, or on 

 muddy shores bordering rivers. It does not (nor does Pomatiopsis) 

 live in large bodies of water such as lakes or rivers. The writer 

 has seen several places in IlHnois, shallow rivulets in woodlands 

 bordering streams, inhabited by these species. One such is near 

 Mahomet on the Sangamon River. Helicodiscus is a typical land 

 mollusk. The character of the deposit (loesslike), the contained 



