338 r. H. KxowLTox — cretaceous-tertiary boundary 



This lot contains a Ginkgo nearest to and probably identical with Ginkgo 

 laramiense Ward, from Point of Eocks, Wyoming, a cycad — PteropJiyl- 

 lum — of a type not found above the Cretaceous, and two species of dicoty- 

 ledons; Viburnum, an unpublished species from Point of Eocks, ajid 

 Platanus ivardii ? Kn., from the lower Montana of the Missouri Eiver 

 below Coal Banks, Montana. 



In my opinion, this collection has a distinct Cretaceous aspect, though 

 it is obviously too small to predicate positively its age. This may explain 

 why the fauna exhibits such an evident affinity with that of the Belly 

 Eiver. I am forced to the conclusion that two very distinct horizons may 

 have been confused under the name of Edmonton. It is just possible that 

 this may be the long lost Laramie fauna. 



This issue can not be avoided, as Doctor Matthew and otliers have pro- 

 posed doing, by extending the definition of Laramie from a formatwn to 

 a group, for then we shall not only contravene the original definition, but 

 we shall have the anomalous condition of the "La ram is group'' being 

 divided by a major unconformity and falling within two systems. The 

 original pronouncement of King, and as emphasized by Cross, Peale, and 

 others, fixes the Laramie as "the uppermost member of the conformable 

 Cretaceous series above the Fox Hills." Being above an unconformity, 

 the "Ceratops beds" are not a part of the "conformable Cretaceous series," 

 and hence can not be Laramie. This condition was correctly appreciated 

 by Barnum Brown, who, in his paper on the "Hell Creek beds," says: 

 "Strictly following King's definition of Laramie, neither of these de- 

 posits ["Hell Creek beds," "Ceratops beds," etcetera] can be considered 

 as such, for neither one represents a continuous sedimentation from the 

 marine Fox Hills. They should therefore be grouped with the Living- 

 ston, Denver, and Arapahoe beds and may be considered post-Laramie." 



It was thought at one time that the ceratopian dinosaurs might be 

 found in the same beds with the Puerco mammals, but, according to Doc- 

 tor Sinclair, apparently this is not so. The Puerco formation rests uncon- 

 formably on dinosaur-bearing beds, beneath which is the ^TLaramie" of 

 the region. I have shown elsewhere, however, that these latter beds are 

 undoubtedly much older than Laramie. The "Ceratops beds," immedi- 

 ately beneath those containing the Puerco fauna, have been practically 

 traced into the Animas formation, which Cross holds is of Denver age. 

 The Animas formation is now kno^^-n to extend eastward to the eastern 

 border of the San Juan basin, near Dulce, Xew Mexico, where it is con- 

 glomeratic at the base and consists of an andesitic matrix, in which are 

 pebbles of many kinds of older rocks ; above this conglomerate axe Eocene 

 leaves. 



