376 HISTORICAL PALEONTOLOGY. 



difficulty in supposing that the Arctic conditions of the Glacial 

 period were immediately followed by anything warmer than a 

 cold-temperate climate ; but there is nothing in the nature of 

 the Mammals themselves which would absolutely forbid their 

 living in a temperate climate. The Hippopotamus major, though 

 probably clad in hair, offers some difficulty since, as pointed 

 out by Professor Busk, it must have required a climate suffi- 

 ciently warm to insure that the rivers were not frozen over in the 

 winter ; but it was probably a migratory animal, and its occur- 

 rence may be accounted for by this. The Wooly Rhinoceros 

 and the Mammoth are known with certainty to have been pro- 

 tected with a thick covering of wool and hair; and their ex- 

 tension northwards need not necessarily have been limited by 

 anything except the absence of a sufficiently luxuriant vege- 

 tation to afford them food. The great American Mastodon, 

 though not certainly known to have possessed a hairy covering, 

 has been shown to have lived upon the shoots of Spruce and 

 Firs, trees characteristic of temperate regions as shown by the 

 undigested food which has been found with its skeleton, oc- 

 cupying the place of the stomach. The Lions and Hyaenas, 

 again, as shown by Professor Boyd Dawkins, do not indicate 

 necessarily a warm climate. Wherever a sufficiency of her- 

 bivorous animals to supply them with food can live, there they 

 can live also ; and they have therefore no special bearing upon 

 the question of climate. After a review of the whole evidence, 

 Professor Dawkins concludes that the nearest approach at the 

 present day to the Post-Pliocene climate of Western Europe 

 is to be found in the climate of the great Siberian plains which 

 stretch from the Altai Mountains to the Frozen Sea. "Covered 

 by impenetrable forests, for the most part of Birch, Poplar, 

 Larch, and Pines, and low creeping dwarf Cedars, they present 

 every gradation in climate from the temperate to that in which 

 the cold is too severe to admit of the growth of trees, which 

 decrease in size as the traveler advances northwards, and are 

 replaced by the grey mosses and lichens that cover the low 

 marshy 'tundras.' The maximum winter cold, registered by 

 Admiral Von Wrangel at Nishne Kolymsk, on the banks of 

 the Kolyma, is 65 in January. ' Then breathing becomes 

 difficult; the Reindeer, that citizen of the Polar region, with- 

 draws to the deepest thicket of the forest, and stands there 

 motionless as if deprived of life ;' and trees burst asunder with 

 the cold. Throughout this area roam Elks, Black Bears, 

 Foxes, Sables, and Wolves, that afford subsistence to the 



