96 GEOGRAPHICAL DISTRIBUTION 



and the Continent, which is shown by geological evidence to have 

 actually been the case. 



The above instances are sufficient to show what an important 

 influence the date of separation of islands from the adjacent 

 continents has had upon their existing mammalian fauna, and how 

 largely the present distribution of mammalian life is bound up with 

 the past history of our globe. We must, however, not omit to 

 mention another very important agency of past times which has 

 likewise had great influence on the present distribution of the 

 various faunas of the northern hemisphere. This is the so-called 

 glacial epoch, which took place immediately before the establish- 

 ment of the present condition of things, and appears to have been 

 the cause of the extinction of many of the larger mammalian types 

 which formerly inhabited Europe, and whose retreat to the warmer 

 regions of the south was apparently cut off by the Mediterranean. 



Zoological Regions. Zoologists are now generally agreed in dividing 

 the land surfaces of the globe into a number of zoological regions or 

 provinces, characterised by a more or less distinctly marked general 

 fades of their fauna as a whole. Some of these regions are much more 

 distinctly defined than the others ; and in the majority of cases 

 there is a kind of neutral ground or No-man's-land at the junction 

 between any two of these regions. It must also be remembered 

 that in the Old World proper as we go back in time we find a 

 gradual assimilation in the mammalian faunas of the different 

 regions, indicating that originally there was one large fauna of 

 a generally similar type occupying the greater portion of this 

 area. Thus we find that Hippopotami, Giraffes, Kudus, Elands, 

 and other types of Antelopes now restricted to Africa, formerly 

 extended to Europe and India, while there is also evidence to show 

 that the group of large anthropoid Apes, now found only in Africa 

 and the Bornean region, were likewise spread over a large part of 

 the south-western half of the Old World. Moreover, while at the 

 present day there is a marked connection between the mammals of 

 the northern regions of both the Old and New Worlds, in the 

 Tertiary period it appears that the fauna of the whole of North 

 America was much more nearly allied to that of the central regions 

 of the Old World than is now the case. Thus in the Tertiary 

 rocks of America we meet with remains of what we are accustomed 

 to regard as such essentially Old World genera as Horses and 

 Rhinoceroses. On the other hand there are no traces in America 

 of the existence at any period of Apes, Giraffes, Hippopotami, or 

 Hyaenas, while that continent has yielded evidence of groups of 

 Ungulates totally unrepresented in the eastern hemisphere. 



The chief zoological regions of the globe, proposed by Mr. Sclater 

 in 1857, and now recognised by the majority of authorities, are 

 six in number, and are named as follows. Firstly, the Palsearctic 



