S4 ROYAL SOCIETY OF CANADA 



and, therefore, from some point farther north in the direction of the 

 headwaters of the streams local to the region. An examination of 

 the adjacent territory is therefore desirable. 



Hanging northward and westward from near the International 

 Boundary, there is an extensive area of 7,500 square miles which Dr. 

 Dawson designated as the Missouri Coteau. Against the southwest 

 side of this area there is another of about 13,000 square miles known 

 as. the Plateau of the Lignite Tertiary. These areas collectively con- 

 stitute the Third Prairie Steppe, the southern face of which lies but 

 a short distance to the north of the 49th parallel.^ From the Plateau 

 of the Lignite Tertiary, the Porcupine Creek flows down to the level 

 of the Second Steppe and crosses the International Boundary at about 

 106 deg. west longitude. Other streams originating in the same 

 plateau flow through the Great Valley at about the 104th meridian. 

 As both these localities are coterminous and represent very nearly 

 the same horizon^- they may be dealt with, for the purposes of the 

 present paper, as essentially one, although as already shown,^ the 

 floras are slightly difl'erent. 1-irom this it will appear within the 

 limits of probability that the water-worn fragments had their origin 

 ■within the area of the Lignite Tertiary Plateau, while tbe others, 

 iound in place, originated near its southern face. 



In his original report u^pon these plants, Sir William Dawson 

 directed attention to the fact that the plants of the Porcupine Creek 

 Group and those of the Great Valley Group are " for the most part 

 identical with those " found common to the Fort Union Series of the 

 United States. They are " also similar to plants collected by Dr. 

 Eichardson in the Lignite Series of the Mackenzie Eiver, as described 

 by Heer, .... they also approach very closely to tne so-called 

 Miocene floras of Alaska and Greenland, as described by Heer; and 

 in their facies and in several of their species, they coincide with the 

 Miocene flora of Europe. If we were to regard the affinities of the 

 plants merely, and to compare them with the Miocene of other coun- 

 tries, and also to consider the fact that several of the species are 

 identical with those still living, anu that the whole facies of the flora 

 coincides with that of modern temperate America, little hesitation 

 would be felt in assigning the formation in which they occur to the 

 Miocene period. On the other hand, when we consider the fact that 

 the lower beds of this formation hold the remains of reptiles of Meso- 

 7oic type, that the beds pass downward into the rocks holding Baccu- 

 lites and Inocerami, and that a flora essentially similar is found 



^ B. N. A. Bound. Comm., 1875, 287-296. 

 == Ibid. App. 327. 

 = Ibid. 



