216 PROF. J. LOGAN LOBLEY, F.G.S., F.R.G.S., ON 
west to Asia, giving two great land bridges by which the 
terrestrial animals of the Old World could travel away from 
their centres of origin, some northwards and westwards and 
some northwards and eastwards, until what is now North 
America was reached, colonised and populated. 
We cannot therefore, I think, hesitate to conclude that, after 
allowing for migrations from the south, much of the fauna of 
the Nearctic region is descended from animals, some of which 
came from Europe by a north-west land extending to Iceland 
and Greenland and on to Labrador, and some of which came 
from Asia by a north-east land extending from Siberia by 
Kamtchatka and the Aleutian Islands to Alaska and Western 
Canada. 
So far I do not think there is anything here stated that will 
be taken exception to by zoogeographers. But now we 
approach a very debatable portion of our subject. This is the 
question of the origin of many animals in North America and 
the West Indies having affinities with species of the 
Mediterranean and North African areas of the Old World, and 
of the South American fauna which is so different from the 
fauna of North America, while it has such strong affinities with 
the fauna of the southern extremities of the land areas of the 
eastern hemisphere. 
On this question eminent authorities differ very widely, and 
the evidence and arguments in support of the different views are 
so important and abundant that it will be impossible to give 
here even the briefest statement of them, but a summary may 
perhaps be attempted. 
The relations existing between South American fossil 
mammals and mammals of the Australian region are very 
pronounced. The discovery of a large number of fossil 
marsupials both in Brazil and Patagonia is of great importance, 
and when it is borne in mind that marsupials are not to be 
found out of America except in the Australian region and that 
only two species, both of the genus Didelphys, are in North 
America, and that, moreover, while the fossil marsupials of 
Europe and the British Islands are of Mesozoic and Eocene ages 
the Patagonian fossils are Miocene, it will be seen that there is 
strong evidence of land connection with the Australian region 
in Tertiary times. 
But in addition to the mammalia, the Patagonian Tertiary 
invertebrate fauna gives 151 species which, with the exception 
of two or three, have not been obtained in North America nor 
indeed in the northern hemisphere, while fifteen are in New 
