INTRODUCTION. 
In the preceding part of our work, we have discussed the 
geographical distribution of animals from the point of view of 
the geographer ; taking the different regions of the earth in 
succession, and giving as full an account as pur space would 
permit of their chief forms of animal life. Now, we proceed 
from the standpoint of the systematic zoologist ; taking in 
succession each of the families with which we deal, and giving 
an account of the distribution, both of the entire family and, as 
far as practicable, of each of the genera of which it is composed. 
As in the former part, our mode of treatment led us to speculate 
on the past changes of the earth’s surface ; so here we shall 
endeavour to elucidate the past migrations of animals, and thus, 
to some extent, account for their actual distribution. 
The tabular headings, showing the range of the family in each 
region, will enable the reader to determine at a glance the 
general distribution of the group, as soon as he has familiarised 
himself, by a study of our general and regional maps, with the 
limits of the regions and sub-regions, and the figures (1 to 4) 
by which the latter are indicated. Much pains have been takeD, 
to give the number of the known genera and species in each 
family, correctly ; but these numbers must, in most cases, only 
be looked upon as approximations ; because, owing to constant 
accessions of fresh material on the one hand, and the discovery 
that many supposed species are only varieties, on the other, such 
statistics are in a continual state of fluctuation. In the number 
of genera there is the greatest uncertainty ; as will be seen by 
the two sets of numbers sometimes given, which denote the 
genera according to different modern authorities. 
