THE FLORA OF JAPAN. 139 



one hundred and twenty feet lower than the ferrugineous sand 

 in which the bones of the Megalonyx Jeffersonii were found." 

 So that they belong to the period immediately succeeding the 

 drift, if not to that immediately preceding it. All the vege- 

 table remains of this deposit, which have been obtained in a 

 determinable condition, have been referred, either positively 

 or probably, to existing species of the United States flora, 

 most of them now inhabiting the region a few degrees farther 

 south. 



If, then, our present temperate flora existed at the close of 

 the glacial epoch, the evidence that it soon attained a high 

 northern range is ready to our hand. For then followed the 

 second epoch of the post-tertiary, called the fluvial by Dana, 

 when the region of the St. Lawrence and Lake Champlain was 

 submerged, and the sea there stood five hundred feet above 

 its present level ; when the higher temperate latitudes of 

 North America, and probably the arctic generally, were less 

 elevated than now, and the rivers vastly larger, as shown by 

 the immense upper alluvial plains, from fifty to three hundred 

 feet above their present beds ; and when the diminished 

 breadth and lessened height of northern land must have given 

 a much milder climate than the present. 



Whatever the cause, the milder climate of the fluvial epoch 

 is undoubted. Its character, and therefore that of the vege- 

 tation, is decisively shown, as geologists have remarked, by 

 the quadrupeds. While the Megatherium, Mylodon, Dico- 

 tyles, etc., demonstrate a warmer climate than at present in 

 the southern and middle United States, the Elephas primi- 

 genius, ranging from Canada to the very shores of the Arctic 

 Ocean, equally proves a temperate climate and a temperate 

 flora in these northern regions. This is still more apparent 

 in the species of the other continent, where, in Siberia, not 

 only the Elephas primigenius, but also a Rhinoceros roamed 

 northward to the arctic sea-coast. The quadrupeds that in- 

 habited Europe in the same epoch are well known to indicate 

 a warm temperate climate as far north as Britain, in the mid- 

 dle, if not the later post-tertiary. North America then had 

 its herds of Mastodons, Elephants,' Buffaloes or Bisons of dif- 



