LANCE FLORA OF EASTERNWYOMING 119 



Here is a typical example of the difficulty encountered when the short-ranging 

 species of an assemblage are too few for reliabiUty. The presence in the flora of 3 

 species of pre-Montanan occurrence is a fair indication that it is somewhat older 

 than any previously discussed. It is to be hoped that larger coUections of plants 

 may be obtained from the Mesaverde formation in order to make its floral assem- 

 blage of greater value for correlation. 



Tullock-Ludlow flora — The contrast between the flora of the type TuUock and 

 Ludlow and the type Lance has previously been pointed out.^ Out of a total of 

 33 species in the type TuUock-Ludlow, there are 21 species with outside distribution, 

 of which only 5 are known also from the type Lance, as is shown in table 3. More- 

 over, these 5 species are aU long-ranging species, 3 from Montanan through Paleo- 

 cene age and 2 from Lancian through Paleocene. Of the total 21 species there are 

 11 that are restricted elsewhere to Paleocene age, 5 that are known in both Lancian 

 and Paleocene age, and 5 that range from the Paleocene into the Eocene or later. 

 It is concluded from these figures that the type TuUock and Ludlow beds, which 

 are non-dinosaur-bearing, are of Paleocene age. 



It has been shown further ^ that other non-dinosaur-bearing beds which else- 

 where overUe the true Lance or HeU Creek formations have at many locaUties 

 yielded plants which are clearly of Paleocene and not Lancian age. These beds are 

 stratigraphicaUy equivalent to the type TuUock-Ludlow beds, which had previously 

 been regarded as the upper member of the Lance formation mainly because of their 

 interfingering relation with the CannonbaU beds, whose marine fauna was regarded 

 as Upper Cretaceous. Recently, however, Fox and Rqss have obtained a large 

 foraminiferal assemblage from the CannonbaU which is correlated with the Paleo- 

 cene Midway of the Gulf Coast.^ Had this correlation been known at the time when 

 the Cretaceous-Tertiary boundary dispute was at high pitch, it seems reasonably 

 sure that Knowlton would not have included the plants of the TuUock, Ludlow, and 

 equivalent beds in his "Lance flora." It would have been apparent that the flora 

 of the true Tnceratops-bearing Lance and HeU Creek beds is quite distinct from 

 that of the overlying non-dinosaur-bearing TuUock, Ludlow, and equivalents. It 

 is now clear that the beUef that the plants of the TuUock, Ludlow, and equivalents 

 belonged to the true Lance was largely responsible for Knowlton's conclusion that 

 this "Lance flora" was essentiaUy a "Fort Union" (Paleocene) assemblage. 



Fort Union flora — As is shown in table 3, there are only 5 species of the Lance 

 flora which occur also in the widespread Paleocene "Fort Union" beds. Only 1 of 

 these species, Cercidiphyllum arcticum, is elsewhere restricted to beds of known 

 Paleocene age; the remaining 4 species are long-ranging forms in both the late 

 Cretaceous and early Tertiary. The detaUed differences between the flora of the 

 type Fort Union and equivalent beds and that of the type Lance has already been 

 reported."' It may here be added that other floras of Lancian age, analyzed above, 

 are Ukewise easily distinguishable from the Fort Union flora or other floras of known 



• Dorf, E., Bull. Geol. Soc. Amer., vol. 51, 223-226. 1940. 



Ubid., 226-232. 



' Fox. S. K., Jr., and Ross, R. J., Jr., Bull. Geol. Soe. Amer., vol. 51, no. 12, pt. 2, 1970, 1940. 



< Dorf, E., op. cit., 217-223, 1940. 



