314 ^he American Geologist. May, i89s» 
No attempt has ever been made in Iowa to subdivide the 
rocks forming the Missourian. In fact the pubhshed informa- 
tion relating to the formations in this state is of the most mea- 
ger description. It has always been referred to in the most 
general way as the Upper Coal Measures. Its unimportance 
as a formation may be further judged from the fact that it 
has generally been regarded as being not more than 200 feet 
thick. 
Recent inquiry has indicated beyond all doubt that there 
are about 1,050 feet of Missourian strata in southwestern Iowa. 
In the same region there are over 450 feet of Des Moines beds. 
These figures are derived from various measurements of sec- 
tions and are corroborated by deep-well records. Although 
the exact distribution of all the Missourian subdivisons has not 
yet been accurately traced, it is now known that all eleven of 
them are present within the limits of the state, except the lola 
and Cottonwood limestone. The course of the Bethany in 
Iowa has been carefully followed by Bain, Leonard and Tilton. 
Other limestones occur to the west of the Bethany border the 
position and relations of which long remained unknown. Nor 
were their distinctions from one another suspected until after 
the succession had been made out carefully on the Missouri 
river. In the deep-well sections of this district the form.ations 
passed through appear to agree very well with what would nat- 
urally be expected to exist. The shales are all very much 
thinner than they are farther southward. The Nodaway coal 
bed, the only seam mined in southwestern Iowa, is in the lower 
part of the Atchison, 75 to 100 feet above the base. The wide 
extent of this coal bed makes it a distinguishing horizon for a 
large area. 
NortJnvcst Missouri Region. In Missouri, the rocks of the 
formations under consideration are better known than in any 
other district. The full thickness of the series is not represent- 
ed within the limits of the state. As for Iowa, about 1,050 
feet may be taken as the actual measurement. The Cretaceous 
rocks nowhere cover the Carboniferous strata, unless it be in 
a few small isolated patches in Nodaway county. Of these, how- 
ever, there is no evidence of existetice. 
The Missourian series forms the surface rock in all, or 
nearly all, of sixteen counties. Small areas occur in at least 
