LANCE FLORA OF EASTERN WYOMING 109 



Rha77im(s? minutus Knowlton.^ The Corbin collection of Hell Creek plants at 

 Princeton University contains excellent specimens of Quercus? vihurnifolia Lesque- 

 reux and Ficusl trincrvis Knowlton, which have not been previously recorded.^ 

 An analysis of the Colgate-Hell Creek fiora gives the following summary : 



No outside distribution 3 



Outside distribution 38 (29 in common with type Lance) 



Total number of species ... 41 



Short-ranging species : Long-ranging species : Species of uncertain range . . 4 



Montanan Montanan-Lancian-Paleocene . 2 



Lancian 18 Montanan-Lancian 10 



Paleocene Lancian-Paleocene 4 



Ts 16 



The short-ranging Lancian species, restricted elsewhere to deposits lying be- 

 tween the Sphenodiscus zone and the top of the Triceratops zone, are as follows: 



Anona? robusta Laurophyllum wardiana 



Carpites lake.sii Magnolia dakotana 



Carpites lancensis Magnolia lakesii 



Cinnamomum? affine Palseoaster inquirenda 



Diospyros berryana Platanophyllum montanum 



Dombeyopsis colgatensis Rhamnus? minutus 



Ficus? ceratops Salix lancensis 



Fraxinus leii Sequoia dakotensis 



Grewiopsis saportana Viburnum marginatum 



This analysis shows that the Colgate-Hell Creek flora is closely comparable 

 with the flora of the type Lance and has a majority of species restricted elsewhere 

 exclusively to beds of Lancian age. As a test case the analysis indicates perfect 

 agreement between plants, vertebrates, marine invertebrates, and stratigraphy in 

 the correlation of the Colgate-Hell Creek beds with those of the Lance formation at 

 its type locality. 



The close relationship of the Colgate-Hell Creek flora to that of the type 

 Lance is seen in the fact that of 38 species with outside distribution, 29 (76 per cent) 

 are known in the type Lance flora. This is a high degree of resemblance and is per- 

 haps somewhat higher than could normally be expected in view of the factors, men- 

 tioned above, which contribute toward preventing absolute identity of contem- 

 poraneous fossil assemblages. 



The time relations here believed to exist between the Colgate-Hell Creek 

 deposits and those of the Lance formation at its type locality are shown in figure 3. 



Medicine Bow flora — In southern Wyoming and adjacent Colorado the Medi- 

 cine Bow formation has yielded a flora of 64 species.'' The plant horizons lie in the 

 lower third of the formation, above Sphenodiscus-hearing Fox Hills sandstone and 



' Sayen, W. H., IH, Tlie Pierre-Fort Union Succession near Glendive, Monlana, senior thesia, Princeton University, 

 14, 32, 41, 59, 1938. 



' Corbin, R. S., Stratigraphy and Paleontology of the Pierre, Fox Hills, and Lance Formationa in Southwestern North 

 Dakota, senior thesis, Princeton University, 19, 20, 97, 115, 1938. 



> Dorf, E., Carnegie Inst. Waah. Pub. No. 508, pt. I, 22-38, 1938. 



