118 
IOWA ACADEMY OF SCIENCES. 
southeastern corner of the county, near the limit of the Wis- 
consin drift, and there are occasional exposures in Franklin 
and Washington townships, along the tributaries of the Skunk 
river and Squaw creek, in the west central portion of the region. 
It is to the latter occurrence that it is desired to direct atten- 
tion. 
The best exposures may be viewed on sections 5 and 34, in 
Washington township, along Clear and Walnut creeks respec- 
tively. 
The Walnut creek section shows: feet. 
Drift, yellowish above, bluish below (Wisconsin) 20 
Loess, sandy below 20 
Clay, blue with much coarse gravel exposed 
The loess is silicious throughout and the upper four feet is 
distinctly joined and stained a faint yellow-brown along the 
joint planes. It grades downward into a massive, structureless, 
pale blue clayey silt which contains, in places, an abundance 
of root casts, wood fragments and black. Carbonaceous spots 
and emits a distinct swamp like odor. The entire deposit is 
highly calcareous and carries a rich gastropod fauna. Prof. 
B. Shimek identified the following forms, the majority of 
which are strictly terrestrial. 
Zonitoides s/wmeA^w,* (Pilsbry) P. & J. 
Sjyliy radium edentulum alticola, (Ingersoll) P. &. J. 
Pupa muscorum, L. 
Bijidaria pentodon, (Say) Sterbi. 
Vertigo ovata, Say. 
Gorulus fulvus^ (Mull). 
Polygyra multilineata^ (Say) P. & J. 
Pyramidula striatella^ (Anth.) P. &. J. 
Vallonia costata, (Mull) Sterbi. 
Succinea lineata, Binn. 
SuGcinea avara, Say. 
Limncea liumilis, Say? 
Loess concretions are relatively scarce and are diminutive in 
size. The deposit shows no signs of oxidation or leaching 
where the drift covering is thick; but where the covering 
is so far reduced as to afford imperfect protection from the 
weathering agents, both leaching and oxidation may be noted, 
and here, alone, are lime concretions to be found. It is obvious 
that little or no alteration took place prior to the deposition of 
the overlying drift. 
