266 THE JOURNAL OF GEOLOGY. 



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 sufificient to constitute a good work- 

 ing 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 Stras- 

 burg, and the leading authority on the subject, and pronounced 

 by him to be a trunk and not a cone (as, indeed I had myself 

 previously stated),^ 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 discov- 

 eries 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. 



Lester F. Ward. 



^ Science, Vol. III., p. 533 (1884). 



