562 Miocene Plants discovered in the Mackenzie River. [June 17, 



Wlien we, moreover, consider that, according to Dawson's determi- 

 nations, one-half the species agree with living forms, while not an 

 individual existing plant is known to occur in the Eocene of Europe, 

 we must certainly range these Porcupine Creek beds with the Miocene 

 and not with the Eocene, where Professor Dawson places them. 



Professor Dawson was led to this incorrect conclusion by some 

 remains of Vertebrata found at Milk River. These, however, occur 

 on a lower horizon than the plant beds on the Porcupine River, as the 

 author himself points out (loc. cit., p. 152), and these Milk River beds 

 may be Eocene. 



Two species are common to the Mackenzie River and Porcupine 

 Creek, and when Professor Dawson, from this circumstance, concludes 

 that the plants from the former locality are Eocene, he has reasoned 

 on entirely mistaken grounds. The same remark may be made when 

 he assigns the Tertiary Flora of the Arctic regions to the Lower 

 Eocene. 



The plant-remains found at Porcupine Creek, on the Mackenzie 

 River, and in Alaska belong to the northern Miocene Flora of North 

 America, which has a considerable number of species in common with 

 the Miocene Flora of the Frigid Zone, and belongs to a period at 

 which in the Rocky Mountains, in Greenland, and Iceland, as well as 

 in Scotland, Ireland, and on the continent of Europe extensive volcanic 

 eruptions occurred, in which these plant-remains are occasionally found 

 embedded. 



If we compare the plants from the Mackenzie River with the 

 Tertiary Flora of the United States, which has been very thoroughly 

 worked up by Professor L. Lesquereux,* we find eight species in 

 common, viz., Tax. dist, Sequ. Langsd., Glyjpt. Ting., Cor. M'Quar., 

 Pop. Richards., Populus Arctica, Behda macrojphylla, and Platanus 

 aceroides (?). 



All these species appear in the Miocene beds of America, but one of 

 them (Pop. Arctica) reaches down into the Oligocene and a second 

 (the Sequoia') possibly even down to the Eocene. 



The comparison with the Tertiary Flora of the United States, 

 therefore, tends to place the white clay beds of the Mackenzie River 

 among the Miocene, and accordingly corroborates the result based on 

 the proved agreement of the fossils therein contained with the Miocene 

 Flora of Europe and of the Arctic regions. 



The specimens of sihcified wood have been submitted for micro- 

 scopic examination to M. C. Schroter, Assistant at the Botanical 

 Laboratory of the Polytechnicum of Zurich, and I shall hope to com- 

 municate a notice of any results he may attain to the Society. 



* L. Lesquereux, "Contributions to the Fossil Flora of the Western Territories. 

 II. The Tertiary Flora." Washington, 1878. 



