Page:The Journal of geology (IA journalofgeology21894univers).pdf/280

that group. But when a rich plant bed was at length discovered at Great Falls it was found to belong to the Kootanie group of Dawson, as developed in regions nearly north of this point. Here then is another series in which the dividing line between the Upper and Lower Cretaceous has to be found.

It would, perhaps, be rash to predict that like conditions will be found to prevail at most points along the slopes of the Rocky Mountains, but the facts are sufficient to constitute a good working hypothesis, and a systematic search at various points in the rocks that overlie the Red Beds and the Jurassic wherever these occur may result in further valuable discoveries. One additional fact that points in this direction may be noted. There was picked up on the surface within the Laramie terrane at Golden, Colorado, a segment of a small cycadean trunk which Lesquereux called Zamiostrobus mirabilis, but which has been sent to Count Solms-Laubach, Professor of Botany at the University of Strasburg, and the leading authority on this subject, and pronounced by him to be a trunk and not a cone (as, indeed I had myself previously stated),^[1] referable to the genus Cycadeoidea. This region, as most geologists know, lies at the foot of the Front Range, and marine Cretaceous passes under the Laramie at Golden. The several members of the Cretaceous, in descending order, would naturally be found in passing up the adjacent slope, and if a horizon yielding cycad trunks occurs here it would be very natural that some of these cylindrical trunks should roll down the steep escarpment and be arrested on the plain below where this specimen was found. This explanation is far more probable than that this form could have grown in Laramie time, though no one can say that this is impossible, especially as the specimen is a diminutive one and may represent the degenerate descendants of the robust forms of the Lower Cretaceous.

Whatever future consequences may grow out of the discoveries recorded in this paper they at least, in and of themselves, constitute a fresh contribution to our rapidly growing knowledge of one of the hitherto least known periods of North American geology, to wit, the Lower Cretaceous.