108 CONTRIBUTIONS TO PAL^ONTOLOGY 



This analysis of the Lance flora is not introduced in order to ascertain its age, 

 since it is obviously of Lancian age as defined. The data will be useful, however, in 

 comparing the analyses of other fioras with that of the Lance. 



The question may be raised as to the significance of the small Paleocene and 

 Montanan elements in the Lance flora. In view of the overwhehning majority of 

 species restricted elsewhere to floras of known Lancian age, it is evident that the 

 4 species previously thought to be restricted in stratigraphic range can no longer be 

 so considered, unless, of course, other investigators should disagree with my identi- 

 fications of these species. Moreover, it is to be expected that future work with 

 floras of Paleocene and Montanan age wiU extend the stratigraphic range of species 

 now known only in floras of Lancian age. 



As will be ampUfied below in the discussion of the Paleocene "Fort Union" 

 flora, the analysis above shows that the flora of the type Lance formation is dis- 

 tinctlj^ not a " Fort Union " assemblage, but is closely related to floras obtained from 

 beds lying between the true Fox HiUs formation and the top of the Triceratops zone. 

 These comprise the Colgate-HeU Creek, Laramie, and Medicine Bow floras, whose 

 analj^ses foUow. These are presented in order to determine the reUabiUty of floral 

 assemblages in the correlation of deposits whose contemporaneity is ah-cady rather 

 definitely estabUshed on the basis of similar stratigraphic position, similar relations 

 to underlying marine invertebrates, and simUar associations with dinosaur remains. 



Colgate-Hell Creek floras — The Colgate flora of eastern Montana and western 

 South Dakota ' is here combined with the HeU Creek flora of the same region for 

 three reasons: (1) Since the Colgate beds lie above the *S'p/ie/iodiscus-beai'ing Fox 

 HiUs marine sandstone, they obviously are of Lancian age as defined. (2) The 

 Colgate beds are lateraUy discontinuous and are seen to interfinger along the strike 

 with the lower beds of the Lance formation as originaUy defined at its type locaUty. 

 (3) The flora of the Colgate beds is distinctly a Lancian flora, containing 13 species, 

 out of 17 species with outside distribution, in common with the type Lance flora; 

 of these 17, 8 are long-ranging species, 6 are restricted elsewhere to Lancian age, and 

 3 are at present of uncertain range but probably Lancian. In this connection it 

 seems significant to montion that the Colgate bcds were originaUy defined as the 

 lower member of the Lance formation.- Their redefinition as a member of the Fox 

 HiUs sandstone ^ docs not seem supported by conclusive facts, particularly in view 

 of the criteria now used elsewhere for the recognition of the upper limit of the Fox 

 HiUs sandstone.* It is felt, however, that whatever the aUocation of the Colgate 

 beds as a Uthologic unit, there should be no coufusion as to their temjioral position. 



The Colgate and HeU Creek floras have been described by Brown,^ and a small 

 HeU Creek flora from South Dakota has been described by Berry.® In the Sayen 

 coUection of Colgate plants at Princeton University there are, besides most of 

 Brown's recorded species, also specimens of Celastrus? taurinensis Ward and 



' Brown, R. W., U. S. Geol. Surv. Prof. Paper 189-1, 242. 1939. 

 ' Calvert, W. R., U. S. Geol. Surv. Bull. 471, 194-195, 1910. 



• Thom, W. T., Jr.. and Dobbin, C. E., BuU. Geol. Soc. Amer., vol. 35, 490, 1924. 



* Lovering, T. S., ct al., Bull. Amer. Assoc. Potrolcum Geologista, vol. 16, 702, 1932. 

 ' Brown. R. W., op. cit., 244, 1939. 



' Berry. E. W., U. S. Geol. Surv. Prof. Paper 18S-F. 127-132, 1934. 



