Introductory Statement. The Comanche series of rocks has been partially described by the writer and others in several previous papers. They represent in time the marine sedimentation between the lacustral land epoch of Permo-Triassic red beds and the upper Cretaceous subsidence begun in the Dakota epoch. Without attempting a minute correlation of its numerous horizons with any beds of the eastern hemisphere, it has been conceded generally that at least the upper portions of this series are of lower Cretaceous age because of their clearly defined stratigraphic position unconformably beneath the Dakota sands, which all authorities have conceded to be of Cenomanian affinities; a conclusion strengthened by the striking paleontologic resemblance of the whole upper Cretaceous (or Meek and Hayden Cretaceous) series to that of Europe. The lower beds of the Comanche series have affinities which entitle them to comparison with the upper Jurassic, while the upper beds have Neocomian . . .