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 Hlephas 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- 
