| I. Niobrara. | II. Benton. | III. Dakota. |
The Cretaceous in Kansas covers an area of over 40,000 square miles, or more than half of the surface of the State. The Pierre and Fox Hill groups of Hayden, and all equivalents of those periods, are entirely wanting. The Cretaceous is, therefore, represented in Kansas, by the Niobrara, Benton and Dakota. The line of demarkation between the Pliocene and Cretaceous, though presenting a very irregular line, is well defined and sharp. Adjoining the Permian easterly, it is not so clear; yet some recent examinations, made in company with Prof. O. St. John, show that the boundary is not difficult to trace. We have never been able to find any fossils of the Jurassic or Triassic, the beds of the Cretaceous resting conformably, or nearly so, on the Permian.
That portion south of the Arkansas river, and west of Harper county, has been little examined, either by myself or others, but appears to be represented by the Fort Benton or Dakota groups.
