350 Tlie American Geologist. June, i89» 
though their exact courses are not yet carefully located. They 
are inferred largely from the succession observed a short dis- 
tance beyond the boundaries of the state in Missouri. 
In southwestern Iowa the general dip of the strata is to- 
wards the west. On the Missouri river a lower anticline 
brings the Plattsmouth limestone again to view opposite Glen- 
wood. All the area east of the river, as far as central Adams 
and Taylor counties, is occupied by the Webaunsee shales. 
One hundred feet above the base of these shales is the Nodaway 
coal seam, that is mined at so many points in Montgomery, 
Page, Adams and Taylor counties. The belt 30 to 4:) miles 
wide, lying to the eastward and reaching to the outcrops of 
the Bethau}' limestone is evidently covered by the other forma- 
tions already mentioned, — the lola excepted. Northward 
from Kansas City the shales are found to become much thin- 
ner. Their thickness in central Iowa is very much less than 
where exposed along the Missouri river. 
Lately a number of deep drill-holes have been put down in 
southwestern Iowa. The records of some of these are suffi- 
ciently accurate to be of much service in checking the succes- 
sion and thickness of the beds composing the Missourian 
series. 
The Cottonwood limestone and the overlying Oklahoman- 
series are not believed to be represented within the limits of 
Iowa. The nearest known exposures are at Auburn, in Ne- 
maha county, Nebraska, and 20 miles from the extreme south- 
west Iowa corner. A large part of the Missourian series, in 
low-a, is overlain by Cretaceous rocks, which extend south- 
ward in a long tongue to within a few miles of the south l^oun- 
dary line of the state. 
According to the most reliable estimate derived from the 
Missouri river section, and from a number of deep wells, the 
greatest thickness of the ]\Iissourian series in Iowa is a little 
over 1,000 feet. This is at the extreme southwest corner of 
the state. The same figures apply to Missouri, the thickest 
point being the extreme northwest corner of that state. The 
thickness of the "lower coal measures," or Des Moines series, 
in the same locality is about 400 feet. 
