72 DISTRIBUTION OF ANIMALS. [part i. 



so clearly indicated as in some of the other regions, and they are 

 adopted more for convenience than because they are very natural 

 or strongly marked. 



The first, or European sub-region, comprises Central and 

 Northern Europe as far South as the Pyrenees, the Maritime 

 and Dinaric Alps, the Balkan mountains, the Black Sea. and the 

 Caucasus. On the east the Caspian sea and the Ural mountains 

 seem the most obvious limit ; but it is doubtful if they form the 

 actual boundary, which is perhaps better marked by the valley 

 of the Irtish, where a pre-glacial sea almost certainly connected 

 the Aral and Caspian seas with the Arctic ocean, and formed 

 an effective barrier which must still, to some extent, influence 

 the distribution of animals. 



The next, or Mediterranean sub-region, comprises South 

 Europe, North Africa with the extra-tropical portion of the 

 Sahara, and Egypt to about the first or second cataracts ; and 

 eastward through Asia Minor, Persia, and Cabul, to the deserts 

 of the Indus. 



The third, or Siberian sub-region, consists of all north and 

 central Asia north of Herat, as far as the eastern limits of the 

 great desert plateau of Mongolia, and southward to about the 

 upper limit of trees on the Himalayas. 



The fourth, or Manchurian sub-region, consists of Japan and 

 North China with the lower valley of the Amoor; and it should 

 probably be extended westward in a narrow strip along the 

 Himalayas, embracing about 1,000 or 2,000 feet of vertical 

 distance below the upper limit of trees, till it meets an eastern 

 extension of the Mediterranean sub-region a little beyond Simla. 

 These extensions are necessary to avoid passing from the Oriental 

 region, which is essentially tropical, directly to the Siberian sub- 

 region, which has an extreme northern character ; whereas the 

 Mediterranean and Manchurian sub-regions are more temperate 

 in climate. It will be found that between the upper limit of 

 most of the typical Oriental groups and the Thibetan or Siberian 

 fauna, there is a zone in which many forms occur common to 

 temperate China. This is especially the case among the phea- 

 sants and finches. 



