II DISTRIBUTION IN THE PAST $3 
period, groups of animals had often a far wider range than 
at present. To-day the Rhinoceroses are limited to Asia and 
Africa, and to quite limited parts of the former continent. 
In the -past, these animals were abundant in Europe and 
North America. Wild Horses now have a range which is not 
widely different from that of the Rhinoceroses, save that they 
extend into the more northern regions of Asia. Their remains 
are abundant both in North and South America. The Hippo- 
potamus, now confined to Africa, once ranged over Europe, 
Madagascar, and India. There were plenty of American and 
European Lemurs. Elephants were nearly world-wide in their 
range; and, in short, restricted distribution seems to be on the 
whole a characteristic of animals of the present day. 
These statements, however, though perfectly true, must not 
lead to erroneous inferences. It is rather impressed upon the 
reader, in books which contain sections dealing with geographical 
distribution, that animals on the whole occupy more restricted 
areas at present than in the past. There are, however, plenty 
of examples of groups of extinct creatures which had, so far as 
we know, quite a restricted range. Thus the Toxodonts were 
purely South American, as were the Glyptodonts and some other 
forms. And, on the other hand, the Cervidae of to-day are as 
widely, if not more widely, distributed than at any other time. 
The Hares and Rabbits are now nearly universal in range; the 
Cats almost so. We meet. with Bovidae, even excluding the Sheep 
and Goats, in all the four quarters of the globe, excluding only 
South America and, of course, Australia. The Camelidae are still 
common to both the Old and the New Worlds. 
During certain periods of the Tertiary epoch it is true that 
there was more similarity between Europe and North America 
than there is at present. It would have been quite necessary to 
unite both into a Holarctic area, such as is now insisted upon by 
many; but the reasons for this union would then have been 
stronger. The fact is, however, that the closer resemblances were 
due to the larger number of families of animals which existed 
then than now; these have decayed away from both continents, 
and allowed ‘the unlikenesses between the mammalian fauna of 
both to become evident. But the likenesses which still sur- 
vive have led many to associate the two regions closely together. 
So far as the history of a genus or family or larger division 
