LANCE FLORA OF EASTERN WYOMING 87 



the region.^ The chief contribution of this report was the observation that the 

 mammaUan remains had been coUected from the same zone that had yielded the 

 dinosaur remains, and were uniformly distributed throughout the entire Lance 

 formation. Emphasizing the relationships of the mammals, LuU regarded these as 

 substantiating the testimony of the dinosaurs for the Mesozoic age of the beds. 



Reports on the structure and the oil and gas resources of the Lance Creek area 

 were pubUshed in 1921 by Hancock,^ and in 1929 by Emery.^ The area between 

 Lance Creek and Newcastle, Wyoming was visited at about this time by Dobbin 

 and Reeside, who convincingly showed that here, as elsewhere, the contact of the 

 Lance formation and the Fox Hills sandstone is essentially transitional.^ This was 

 an important observation, since by this time proponents of the contention that the 

 Lance formation belongs in the Cenozoic had stressed the presence of a major un- 

 conformity at the top of the Fox Hills. 



The report by Dobbin and Barnett ^ on the GUlette coal field, which Ues just 

 north of the Lance Creek area, contains observations of significance to the present 

 report. The Lance formation in that region is subdivided by Dobbin and Barnett 

 into two members, which "are respectively correlated with and are directly trace- 

 able northward into the Hell Creek and TuIIock members of the Lance formation as 

 recognized in eastern Montana. The Hell Creek member is also traceable south- 

 eastward into the ' Ceratops beds ' of the Lance Creek area, described by Hatcher and 

 by Stanton and Knowlton." ^ This clearly implies, as I have also noted in a visit 

 to the area, that the TuIIock member of the Lance, which overlies the Hell Creek, is 

 directly traceable southeastward into the well-recognized Fort Union beds of the 

 Lance Creek area. This is in agreement with the evidence of the fossil plants, as 

 discussed elsewhere in this report, that the TuIIock is Paleocene "Fort Union," and 

 not a part of the Lance formation as originally defined. 



The mammalian remains of the Lance Creek area were included in Simpson's 

 monograph on American Mesozoic mammals,^ pubUshed in 1929. The Lance mam- 

 maUan fauna is regarded (fig. 61 of Simpson) as of latest Cretaceous age. The dino- 

 saurs of the area were again discussed in 1930 by RusseU,* who listed the nineteen 

 species known and discussed their relation to other faunas. He concluded that the 

 Lance formation, as originally defined in the Lance Creek area, is equivalent in 

 Montana and the Dakotas to only the Hell Creek beds, and that the TuUock and 

 Cannonball should be provisionally included in the Paleocene. This opinion is now 

 beUeved to be substantiated by the positive evidence of the fossU plants of the 

 present report. 



In the past decade the Lance Creek area has not often been the subject of dis- 

 cussion. In 1933 LuII included a systematic treatment and discussion of the dino- 



• LuU. R. S., Amer. Jour. Sci., 4th ser., vol. 40, 319-348. 1915. 

 ' Hancock. E. T., U. S. Geol. Surv. Bull. 716, 91-122, 1921. 



' Emery, W. B., Amer. Assoe. Petroleum Geologists, Structure of Typical Amcrican Oil Fields, vol. 2, 604-613, 1929. 



* Dobbin, C. E., and R«eside, J. B., Jr., U. S. Geol. Surv. Prof. Paper 158-B, 18-20, 1929. 

 ' Dobbin, C. E., and Barnett, V. H., U. S. Geol. Surv. BuU. 796-A, 1-50, 1927. 



« Ibid., 8. 



' Simpson, G. G., Mem. Peabody Mus. Nat. Hiat., vol. 3, pt. 1, 97-139, 146, 149, 150, 1929. 



' RusseU, L., Proc. Amer. Philos. Soc, vol. 69, 139-141, 1930. 



