1872.] DAWKINS CLASSIFICATION OF PLEISTOCENE STRATA. 441 



and those which were living in the same area in the Pliocene age. 

 The migration of the first two groups into Europe at the close of 

 the Pliocene age throws a very great light on the ancient geography. 

 Had not the animals which lived in Europe during the Pliocene 

 age heen insulated by some physical barrier from those which invaded 

 Europe from Asia, the latter would occur in our Pliocene strata 

 as well as the former, and we might have had the mammoth and the 

 mastodon associated here as well as in North America. Such a bar- 

 rier is offered by the northern extension of the Caspian along the 

 low-lying valley of the river Obi; and that the Caspian has extended 

 further north than now in comparatively modern times has been 

 proved by Dr. Pallas. It is therefore very probable that this was 

 the barrier which divided the Pliocene mammalia of Europe from 

 those animals which were living at the time in Asia, and which 

 subsequently passed into Europe. The animals of Northern and 

 Central Asia could not pass westwards before this barrier was re- 

 moved by the elevation of the sea-bottom between the Caspian sea 

 and the southern portion of the Urals. When this took place the 

 Musk-shrew, Lemming, Brown and Grizzly Bears, Mammoth, Woolly 

 Ehinoceros, Musk-sheep, Keindeer, Stag, and Roe passed over into 

 JEurope *, those of them which were fitted for a temperate or mo- 

 derately warm climate, such as the Stag, Roe, Brown and Grizzly 

 Bears, passing down to the extreme southwest, while the rest did 

 not go further to the south than the Alps and Pyrenees. Then 

 there must have been a continuous mass of land extending from 

 Northern Asia to the margin of the Atlantic, which has been proved 

 by Mr. Godwin -Austen and others to have passed from Scandinavia 

 to the west of the present coast-Hne of Ireland, of the south of Eng- 

 land, and of France. [See Map, p. 436.] 



18. The Sotjthekn Extension of Eiteope. 



The same argument may be based on the African mammalia. 

 The African Elephant could not have found its way northwards to 

 Spain and Sicily, or the Serval to Spain, or the Felis caffer to Britain 

 without an extension of the African mainland, so as to allow of the 

 migration ; and the same may be said perhaps of the Spotted Hysena, 

 although this animal, so widely spread through Central and Southern 

 Europe, may have arrived by way of Asia Minor, as well as by a 

 direct line, passing through Sicily and Gibraltar. Nevertheless, as 

 Dr. Falconer has remarked, the area of the Mediterranean must have 

 been very much smaller than it is now during the time that Malta, 

 Sicily, and Candia were inhabited by the Pleistocene mammalia. 

 The presence of Hippopotamus Pentlandi in these three islands 

 proves that they were connected during the life-time of the animal ; 

 and this mass of land would afford a passage northwards to the 

 African mammalia. The objection which is offered by the depth of 



* This is very nearly the same view as that held by Dr. Brandt, Imp. Acad. 

 St. Petersb., ' Zoogeographische und Palaontographische Beitrage,' April 4, 

 1867. See also Lartet, ' Coraptes Bendus,' tome IxtI. p. 409. 



