ANNIVERSARY ADDRESS OF THE PRESIDENT. lvii 
It is unfortunate that we have no knowledge of the Miocene 
mammalian fauna of the Australian and Austro-Columbian pro- 
vinces; but, seeing that not a trace of a Platyrrhine Ape, of a Pro- 
eyonine Carnivore, of a characteristically South-American Rodent, 
of a Sloth, an Armadillo, or an Anteater has yet been found in Mio- 
cene deposits of Arctogeea, I cannot doubt that they already existed 
in the Miocene Austro-Columbian province. 
Nor is it less probable that the characteristic types of Australian 
Mammalia were already developed in that region in Miocene times. 
But Austro-Columbia presents difficulties from which Australia is 
free ; Camelide and Tapiride are now indigenous in South America 
as they are in Arctogeea, and among the Pliocene Austro-Columbian 
mammals, the Austro-Columbian genera Equus, Mastodon, and Ma- 
chairodus are numbered. Are these Postmiocene immigrants, or 
Przmiocene natives ? 
Still more perplexing are the strange and interesting forms J’oxo- 
don, Macrauchenia, and Typotherium, and a new Anoplotherioid 
mammal ( Homalodotherium) which Dr. Cunningham sent over to me 
some time ago from Patagonia. I confess I am strongly inclined to 
surmise that these last, at any rate, are remnants of the population 
of Austro-Columbia before the Miocene epoch, and were not derived 
from Arctogzea by way of the north and east. 
The fact that this immense fauna of Miocene Arctogea is now 
fully and richly represented only in India and in South Africa, while 
it is shrunk and depauperized in North Asia, Europe, and North 
America, becomes at once intelligible, if we suppose that India and 
South Africa had but a scanty mammalian population before the 
Miocene immigration, while the conditions were highly favourable 
to the new comers. It is to be supposed that these new regions 
offered themselves to the Miocene Ungulates, as South America and 
Australia offered themselves to the cattle, sheep, and horses of 
modern colonists. But, after these great areas were thus peopled, 
came the Glacial epoch, during which the excessive cold, to say 
nothing of depression and ice-covering, must have almost depopulated 
all the northern parts of Arctogeea, destroying all the higher mam- 
malian forms except those which, like the Elephant and Rhinoceros, 
could adjust their coats to the altered conditions. Even these must 
have been driven away from the greater part of the area; only 
those Miocene mammals which had passed into Hindostan and into 
South Africa would escape decimation by such changes in the 
physical geography of Arctogeea. And when the northern hemi- 
sphere passed into its present condition, these lost tribes of the 
Miocene Fauna were hemmed by the Himalayas, the Sahara, the Red 
Sea, and the Arabian deserts within their present boundaries. 
Now, on the hypothesis of evolution, there is no sort of difficulty 
in admitting that the differences between the Miocene forms of the 
mammalian Fauna and those which exist now are the results of gra- 
dual modification ; and, since such differences in distribution as ob- 
tain are readily explained by the changes which have taken place in 
the physical geography of the world since the Miocene epoch, it is 
