302 The American Geologist. May.i899 
features of geographic distribution, topographic expression, 
Uthologic nature, stratigraphic delimitation, biologic defini- 
tion, and economic content, which go to characterize and con- 
trast geological formations, the Missourian series is clearly set 
off from all associated strata. 
Its areal range and geological position are intermediate be- 
tween the Des Moines series on the one side and the Oklaho- 
man 6n the other. 
The topographic expression of the area occupied by the 
Missourian strata is of a wholly different type from that of the 
Des Moines or that of the Oklahoman. The latter are soft 
rocks and the general aspect of the countr\- is a lowland plain of 
faint relief. In the case of the Missourian area there is an al- 
ternation of hard and soft beds ; the strata are slightly inclined 
westward and the whole region is bevelled off. The new cycle 
of erosion that has begun has not worn down the rocks equally. 
The hard members are left in relief. A series of escarpments, 
nearly parallel to one another is formed. These face east- 
ward; that is, the steep side is in that direction, and the gentler 
backslope is in the opposite direction. The latter soon merge 
into the lowland areas between the ridges, worn out on the soft 
rocks. It is essentially the step and platform topography, or, 
as it is more gracefully termed, cuesta relief. 
In lithological characters the Missourian beds are chiefly 
limestones and calcareous shales. They thus differ from those 
of the Des Moines series, which are largely argillaceous or 
sandy shales, and from those of the Oklahomxan, which are like- 
wise near -shore deposits. Next to the Mississippian, the Mis- 
sourian beds are the most strictly marine deposits of all the 
Carboniferous of the region. The fauna is also strictly mari- 
time. 
In economic content the almost total absence of coal puts 
the Missourian series in marked contrast with the Des Moines. 
Base of the Missourian. The lower limiting horizon of the 
Missourian series is the bottom of the Bethany limestone. In 
all features it is one of the most pronounced lines of deniarka- 
tion in the whole Carboniferous system as represented in the 
continental interior. The limestone itself is the most important 
al)ove the Mississippian. Below it. through all the Des Moines 
