64 DISTRIBUTION OF ANIMALS. [PART I. 
the antipodes of each other, would be most inconvenient, even 
if there were not such difference of opinion about them. There 
can be little doubt, for example, that the most radical zoological 
division of the earth is made by separating the Australian re- 
gion from the rest; but although it is something useful and 
definite to know that a group of animals is peculiar to Australia, 
it is exceedingly vague and unsatisfactory to say of any other 
group merely that it is extra-Australian. Neither can it be said 
that, from any point of view, these two divisions are of equal 
importance. The next great natural division that can be made 
is the separation of the Neotropical Region of Mr. Sclater from 
the rest of the world. We thus have three primary divisions, 
which Professor Huxley seems inclined to consider as of 
tolerably equal zoological importance. But a consideration of 
all the facts, zoological and paleontological, indicates, that the 
great northern division (Arctogza) is fully as much more impor- 
tant than either Australia or South America, as its four compo- 
nent parts are less important ; and if so, convenience requires 
us to adopt the smaller rather than the larger divisions. 
This question, of comparative importance or equivalence of 
value, is very difficult to determine. It may be considered from 
the point of view of speciality or isolation, or from that of 
richness and variety of animal forms. In isolation and speciality, 
determined by what they want as well as what they possess, the 
Australian and Neotropical regions are undoubtedly each com- 
parable with the rest of the earth (Arctogeea). But in richness 
and variety of forms, they are both very much inferior, and are 
much more nearly comparable with the separate regions which 
compose it. Taking the families of mammalia as established by 
the best authors, and leaving out the Cetacea and the Bats, 
which are almost universally distributed, and about whose 
classification there is much uncertainty, the number of families 
represented in each of Mr. Sclater’s regions is as follows : 
I. Palearctic region has 31 families of terrestrial mammalia. 
ine Ethiopian ” ” 40 ” ” ” 
IIJ. Indian ” ” 31 ” ” ” 
IV. Australian ” ” 14 ” ” ” 
V. Neotropical ,, », 26 ” ” ” 
VI. Nearctic “o 9) 23 ” ” ” 
