132 KANSAS ACADEMY OF SCIENCE. 
the literature of the group. Passing by the exposures which are known to occur 
in Minnesota, South Dakota, Wyoming, Colorado, Oklahoma, New Mexico and 
other states, I shall at once proceed to consider the Kansas-Nebraska outcrops 
of the Dakota. 
In general, the formation as exposed in the region extends in a line from 
Sioux City, Iowa, to Ashland, in southwestern Kansas. The distance as the 
crow flies is not far from 500 miles. The width of the group, as exposed, proba- 
bly averages about thirty-five miles, although places may be found where the 
distance from the eastern to the western limits is to exceed eighty miles. Both the 
lower and upper lines of outcrop are exceedingly irregular. The subjacent for- 
mations extend far up the valleys, and in places approach within a few miles of 
the Benton, which, resting on the Dakota, caps the hills to the west. A good 
example of this fact may be seen in western Saline and eastern Ellsworth coun- 
ties, Kansas. From Brookville, which is near the top of the Permian, to the 
noted cave section, on the hills back of which the Benton may be found, is less 
than ten miles, although in the intervening country may be found some of the 
roughest and most typical Dakota in the two states. Another instance is near 
the Kansas-Nebraska line. The Permian is found as far up the Little Blue river 
as Steel City; while the Benton on the hills to the west is not more than six 
miles distant. 
In the following discussion I shal! consider that the line of unconformity at 
the base of the Cretaceous rests, respectively, on three phases of the Upper 
Paleozoic rocks: Upper Carboniferous, Permian, and Triassic; that the horizons 
just mentioned are conformable throughout; that the Comanche series, or Lower 
Cretaceous of Kansas, is found only in the southern and central parts of the 
state; that it consists of two formations—the Cheyenne sandstone, confined to 
the Belvidere locality, and the Kiowa shale, known in the central part of the state 
by the term ‘‘Mentor Beds’’; that the Dakota rests conformably on the Lower 
Cretaceous wherever the latter is exposed; and that it passes conformably above 
into the Benton, which consists of shales and fossiliferous limestones. These 
topics are treated at greater length under their proper head, stratigraphy, and 
are introduced here simply in order that the subject may be understandingly 
read. 
In order to simplify the discussion of the various outcrops, I have divided the 
entire region into three areas, viz.: The southern Kansas area, the Smoky-Blue 
area, and the Nebraska area. The first of these occurs in southwest Kansas, 
and contains the following four localities: Belvidere, Clark county, Cimarron- 
Bear, and Arkansas localities. The second area extends from the Arkansas 
river, at Great Bend, to the Big Blue river, near Beatrice, Neb. In the discus- 
sion it will not be subdivided. The third area, which lies for the most part in 
eastern Nebraska, consists of the Salt Creek, Platte, Missouri,and Big Sioux 
localities. This division differs essentially from that of Doctor White, who in- 
cludes in his ‘‘Southern Interior” region all the formations south of the Platte 
river, and in the ‘‘ Northern Interior’’ region all lying north of this stream. It is 
obvious that both of these divisions are purely arbitrary, and have been adopted 
simply as a convenient schedule of classification. My divisions, in particular, 
are purely local, and are nothing but convenient groupings for purposes of dis- 
cussion. 
The exposures of the Dakota of the first or southern Kansas area are overlaid by 
the Tertiary, and grade conformably upward from the Comanche. The Dakota 
of the second area rests conformably on the Comanche, or unconformably on the 
Permian, and is capped with the Benton, except in southern Nebraska, where 
