LIFE IN TERTIARY TIMES 283 



site of the Alps and reached the basin of Vienna, the Baltic 

 area, etc., and sometimes leaving only a few narrow channels, 

 until the time when the Mediterranean was to take its present 

 form. 



During the Neogene Period, the European and the Sino- 

 Siberian continents united, never again to separate, so that 

 the Mammals of Asia easily passed over to Europe, and it 

 was moreover through Asia that African animals migrated 

 into Europe. North America and Asia were still in communica- 

 tion by way of Spitzbergen and Greenland, but an arm of 

 the sea separated Europe from the Arctic continent. North 

 and South America were separated ; the latter ceased thence- 

 forth to be united to Africa, and Madagascar became isolated 

 from India and Australia. The hypothetical Pacific continent 

 seems to have disappeared under the water. Summing up 

 these data we find that there was now an Arctic Ocean 

 separated from the Atlantic by the continent which included 

 North America, Spitzbergen, and Greenland, and which 

 was connected to Asia ; and that the present Atlantic, Pacific, 

 and Indian oceans were now definitely constituted. 



During the Eogene Period, the alternate rising and sinking 

 of the land surface allowed the passage of ocean currents, 

 flowing sometimes from the Arctic and sometimes from tropical 

 seas, and this brought about a more or less durable fall or 

 rise of temperature along the coasts, although the mean 

 remained relatively high. The oldest known flora of this 

 Period, the Gelinden, 1 contains Willows, Cupuliferae, 2 

 Ranunculaceae, 3 Laurinaceae, Celastrinacese, Menispermaceae, 

 etc., which still recall the Cretaceous flora. A little later 4 

 the petrifying spring of Sezanne encrusted the flowers, leaves 

 and fruits of plants which are found to-day, some in temperate 

 and others in tropical regions, and still later a definitely 

 tropical flora flourished in the Isle of Wight. 5 The climate 

 must therefore have become hot again. The tropical flora 

 was maintained still later 6 in the sandstone formations at 

 Sabalites in the region of Maine and in the south of England. 7 

 At the end of the Tertiary Era 8 the mean temperature of 



1 Lower Thanetian. 2 Dryophyllum. 



3 Dewalquea. * Upper Thanetian. 



5 Lutetian. 6 Auversian. 



7 Lattorfian. 8 Neogene. 



