OF UPPER EOCENE CLIMATES. 5 



although there is also something to be said for the latter. Heer 

 studied these Arctic floras after his monumental v/ork on the Tertiary- 

 floras of Switzerland, and he called them Miocene, a fashion that still 

 persists in some quarters. It is lost sight of that Heer was prone to 

 see his familiar Swiss Tertiary species in what were often very im- 

 perfect fragments from the far North ; and it is also true that Heer 

 recognized no Oligocene period, but included the fossils of this age 

 in the Miocene, which, to that extent, never meant more than " old 

 Miocene " — that is to say, Oligocene. 



The " Arctic Miocene " flora is certainly younger than that of our 

 Fort Union of the western United States and Canada, whose facies 

 continues into the Wasatch of the same region. It is overlain in 

 places by marine Miocene strata, and interbedded with upper Eocene 

 marine faunas, as at Herendeen Bay, Alaska. I have been inclined 

 to consider it as also younger than the Green River flora of the west- 

 ern United States, and to be of approximately the same age as the 

 Jackson flora of the southern Atlantic Coastal Plain. It is certainly 

 older than any known lower Miocene flora of the United States or 

 Europe, and the following comparisons do not suffer any diminution 

 of conclusiveness, if the Arctic flora should eventually be proven to 

 be slightly older or slightly younger than the Jackson, for we now 

 know as considerable floras in the southern Coastal Plain from the 

 immediately antecedent Claiborne group, and from the immediately 

 subsequent Oligocene (Catahoula and Vicksburg), and all of these 

 have substantially the same facies and climatic significance as has the 

 flora of the Jackson group. 



The Jackson flora, a detailed account of which is in press as Pro- 

 fessional Paper 92 of the United States Geological Survey, contains 

 considerably over one hundred species. These represent genera such 

 as Acrostichum, Pistia, Canna, Thrinax, Phcenicites, Engelhardtia, 

 Momisia, Ficus, Coccolohis, Pisonia, MyrisHca, Anona, Inga, Cassia, 

 Banhinia, Sophora, Lonchocarpus, Fagara, Cedrela, Banisteria, Biir- 

 serites, Cupanites, Dodoncea, Grewiopsis, Bomhacites, Ternsfrcemites, 

 Cinnamomum, Mespilodaphne, Nectandra, Rhisophora, Terminalia, 

 Conocarpus, Conhretum, Myrcia, Calocarpum, etc. There is not a 

 distinctly temperate type among them and this flora comes as near 

 meriting the term " tropical " as any fossil flora known from the 



