chap, x.] THE PALiEARCTIC REGION. 181 



tions of convenience, dependent on custom and on the more or 

 less perfect knowledge we possess of some of the intervening 

 countries. 



Zoological Characteristics of the Palmarctic Region. — The Palae- 

 arctic region has representatives of thirty-five families of 

 mammalia, fifty-five of birds, twenty-five of reptiles, nine of 

 amphibia, and thirteen of freshwater fishes. Comparing it with 

 the only other wholly temperate region, the Nearctic, we find a 

 much greater variety of types of mammalia and birds. This 

 may be due in part to its greater area, but more, probably, 

 to its southern boundary being conterminous for an enormous 

 distance with two tropical regions, the Ethiopean and Oriental ; 

 whereas the Nearctic has a comparatively short southern bound- 

 ary conterminous with the Neotropical region only. This is so 

 very important a difference, that it is rather a matter of surprise 

 that the two north temperate regions should not be more unequal 

 in the number of their higher vertebrate forms, than they 

 actually are. 



It is also to the interblending of the Palsearctic with the two 

 adjacent tropical regions, that we must attribute its possession 

 of so few peculiar family groups. These are only three ; two 

 of reptiles, Trogonophidcc and Ophiomoridce, and one of fishes, 

 Comephoridm. The number of peculiar genera is, however, con- 

 siderable, as the following enumeration will show. 



Mammalia. — The monkey of Gibraltar and North Africa, and 

 an allied species found in Japan, are now considered to belong 

 to the extensive eastern genus Macacus. The former, however, 

 is peculiar in the entire absence of the tail, and has by many 

 naturalists, been held to form a distinct genus, Inuus, confined 

 to the Palsearctic region. 



Of bats there are one or two genera (Barbastelhis, Plecotus) 

 which seem to be mainly or wholly Palsearctic, but the classifi- 

 cation of these animals is in such an unsettled state that the 

 distribution of the genera is of little importance. 



In the next order, Insectivora, we have almost the entire 

 family of the Moles confined to the region. Talpa just enters 

 Northern India ; and Urotrichus is common to Japan and North- 



