ol 
indicated by the flora. In this category is to be placed the 
Green River Tertiary beds, those of Mississippi studied by 
Lesquereux, and those of Brandon, Vermont. In the 
Miocene the continental surface was broader, the western 
lakes were fresh and the vegetation very much like that of 
the present day. A few palms then grew as far north as the 
Yellow Stone River, and a flora flourished im Alaska and 
Greenland as varied and as luxuriant as now grows along the 
fortieth parallel. At this time land connected Hurope, this 
continent and China, as the flora in this region was essentially 
the same, a large number of plants being common to the 
three continents. The mammals were peculiar; over our 
western plains rolled herds of great quadrupeds rivaling in 
number and variety those of southern Africa at the present 
time. This state of things continued during the Pliocene age 
and up to the ice period. In the middle Tertiary the 
climates of Alaska and Greenland were those of New York 
and St. Louis at present. ‘Then came the Glacial epoch, and 
the climate of Greenland of the present time is brought down 
to New York and all the northern portion of the continent is’ 
wrapped in ice. This change of climate was gradual, but the 
animals and vegetables were driven southward until the 
glaciers reached the thirty-eighth or fortieth parallel when a 
temperate climate prevailed in Mexico and only on the 
southern border would the temperature be what it had 
previously been on our northern border. Thus nearly all the 
animals were exterminated or forced into very narrow limits 
in southern Mexico. 
Plants bore their expatriation better, and as a consequence 
we find the present flora of our continent much more like 
that of the Miocene than is our fauna, though most of the 
forest-trees have become extinct. Of these the Glyptostrobus 
1s an example, which grew all over our continent and 
northern Hurope. In the glacial period it was exterminated 
except in China where it now grows. So when we compare 
the present flora of China and Japan with that of the eastern 
half of our continent we find the strongest proofs of their 
relationship ; many species are identical, while others are but 
