LANCE FLORA OF EASTERN WYOMING 113 



The representation in figure 3 of the age relations of the Laramie and the over- 

 lying Arapahoe-Denver and Dawson formations is based on an opinion derived from 

 combination of the evidence of the vertebrates, the plants, and the stratigraphic 

 succession. The placing of the exact horizon marking the Upper Cretaceous- 

 Paleocene boundary in the Denver and Dawson beds, if it is determinable at all, 

 must await further work in the region. 



Black Buttes " Laramie" flora — The flora from near Black Buttes in south- 

 western Wyoming has been discussed ^ in my report on the Medicine Bow fiora, 

 to which it is closely related. The plant-bearing beds near Black Buttes overlie a 

 massive coarse sandstone tentatively called " Fox Hills." Diagnostic invertebrates 

 of true Fox Hills age are lacking, however, although the fauna of the underlying 

 Lewis shale is clearly of late Montanan age." Remains of a single species of dino- 

 saur, Agathaumas sijlvestris Cope, were collected from the same beds that contain 

 the plant horizons.^ The unique characters of this ceratopsian dinosaur make it 

 rather unreUable for exact age determination, except, of course, as it places the 

 beds in the Upper Cretaceous and not the Paleocene. The floral assemblage must 

 therefore be the chief basis for correlation at the present time. 



The latest complete floral list of plant species from the Black Buttes " Laramie " 

 was given by Knowlton in 1919.* Aflowing for subsequent synonymies, this as- 

 semblage may be analyzed as follows : 



No outside distribution 19 



Outside distribution 31 (22 in common with type Lance) 



Total number of species ... 50 



Short-ranging species : Long-ranging species : Species of uncertain range . . 7 



Montanan Montanan-Lancian-Paleocene . 1 



Lancian 13 Montanan-Lancian 6 



Paleocene Lancian-Paleocene 4 



l3 Tl 



With a total of 22 species (71 per cent), out of 31 species with outside distribu- 

 tion, in common with the type Lance flora, the Black Buttes "Laramie" is clearly 

 of true Lancian age. This is further corroborated by the 13 short-ranging species, 

 all of which are elsewhere restricted to deposits of known Lancian age. These 

 species are as follows: 



Apeibopsis? discolor Menispermites cockerelli 



Carpites glumaeformis Pisonia? racemosa 



Carpites verrucosus Platanophyllum platanoides 



Cissus? lobato-crenata Sabalites eocenica 



Grewiopsis saportana Saliciphyllum wyomingensis 



Laurophyllum coloradensis Viburnum marginatum 

 Laurophyllum meeki 



'Ibid. 



' Stanton, T. W., and Knowlton, F. H., Bull. Geol. Soc. Amer., vol. 8, 146, 147, 1897. 



' Hatcher, J. B., and Lull, R. S., op. cit., 104, 1907. Lull, R. S., op. cit., 15, 1933. Stanton, T. W., Proc. Washington 

 Acad. Sci., vol. 11, 270, 1909. 



* Knowlton, F. H., U. S. Geol. Surv. Bull. 696, 767, 1919. 



