226 GLACIAL HISTORY. 



general way how it happened that Europe, in the Miocene 

 epoch, possessed a whole series of plants and animals the 

 nearest allies * of which now belong exclusively to North 

 America, and that some types of animals and plants of the 

 Tertiary epoch (vol. i. pp. 348 & 370), as well as some American 

 types, have maintained themselves to the present day in the 

 Atlantic islands. Probably the depression of the great Miocene 

 continent, which has here been designated under the name of 

 Atlantis, was contemporaneous with the elevation of the Alps, 

 and the sinking of the land continued until the close of the drift 

 epoch. By this depression the continuity of Europe and Ame- 

 rica became broken ; and whilst during the Miocene period 

 the organic world of Europe possessed numerous American 

 types, these disappeared during the drift period. Their place 

 was taken by species of plants and animals coming from the 

 east, which constitute the greater part of the flora and fauna of 

 the Swiss plains ; and the Alps received numerous immigrants 

 of Scandinavian origin, which now form an integral part of the 

 Swiss Alpine flora. 



Organic nature does not seem to have undergone in America 

 so strongly marked a change as in Europe. The existing 

 American flora much more closely resembles the Miocene flora 

 both of America and of Europe. Tertiary types may be more 

 easily preserved, owing to the form of the American continent, 

 which stretches through both hemispheres, and consists of im- 

 mense territories not for a long period invaded by the sea ; whilst 

 the contour of Europe is indented, and its area is of smaller ex- 

 tent, so that the Tertiary types have been in great measure 

 destroyed. A certain number of these types, however, have 

 maintained their ground in the Mediterranean zone, and have 

 become the parent plants which bind the flora of that zone to 

 the Tertiary flora. 



Is the Atlantic continent, the existence of which we have just 

 assumed in accordance with the facts stated, the same as the 



* In this question, the analogy of the species has quite a different bearing 

 from that of the genera ; which Prof. Oliver seems to have forgotten in his 

 treatise,. " The Atlantis hypothesis in its Botanical aspect," Nat.-Hist. Rev. 

 1862. 



