Some time ago, while working on a problem that involved the question of the presence or absence of islands near the close of the Cretaceous period in the region now occupied by the southern part of the Rocky Mountains, I was forced to the conclusion that no land masses or islands of any considerable size persisted there throughout the Cretaceous period, for I found no sedimentary rocks that were clearly derived from such islands. This result led to a reexamination of available information to see what evidence the sedimentary rocks in other areas near the present mountains could furnish, and I found rather unexpected confirmation of my conclusion. In the course of this study it became evident t that there is apparent conflict of testimony between different classes of fossils and that the physical evidence, including lithology, structure, and sequence of beds, is at variance with some of the commonly accepted correlations. In this state of uncertainty I tried to apply physiographic principles to see if they would throw any light on the interrelations of the interrelations of the Cretaceous formations of the Rocky Mountain region and on the events that opened and closed the period. This led me to a conclusion similar to that reached by the paleontologist C. A. White many years ago, namely, that the Upper Cretaceous formations up to and including the Laramie extended across the site of the mountains.
