94 GEOGRAPHICAL DISTRIBUTION 
to India and Africa. The American Puma, again, may be cited as 
an example of a mammal having a very wide range in latitude, 
since it is found from Patagonia in the south to Canada in the 
north. As instances of wide range in the opposite direction we 
have only to mention the Reindeer and the Elk or Moose, found 
in the northern regions of both the Old and New Worlds, which 
are only separated from one another by the narrow channel of 
Behring Strait. 
Of mammals with extremely restricted distributional areas, we 
may mention many of the Insectivora, such as the Desman of the 
Pyrenees, and some of the Madagascar types of this order, the 
Lemurs from the same island, some of the species of Marmots, the 
remarkable bear-like Aluropus of Eastern Tibet, one species of Zebra, 
and other Ungulates from Africa. 
The distribution of a genus (except of course when the genus is 
represented only by a single form) is very generally more exten- 
sive than that of a species; and this may be markedly the case 
when there are only some two or three species in a genus. In 
genera, moreover, we meet with what is known as discontinuous 
distribution, that is, where the distributional area of one or 
more’ species is totally separated from that of others. The best 
instance of this occurs in the case of the Tapirs, where we find 
one species inhabiting the Malayan Peninsula, and no others 
anywhere in the world, with the exception of South America. The 
explanation of such an apparently anomalous feature in distribution 
is to be found in the past history of the globe, which shows us that 
Tapirs once existed in China, Europe, and North America, and, 
therefore, indicates that the existing isolated species are the sole 
survivors of a group once spread over a large portion of the earth’s 
surface. In regard to generic distribution it must, however, be 
mentioned that this depends to a great extent on the limits which 
we are disposed to assign to genera themselves. 
As the distributional area of a genus generally exceeds that of 
a species, so that of a family, or group of genera, is larger than that 
of a single genus; and similarly the distribution of an order, or 
assemblage of families, usually occupies a larger area than that of 
a single family. Thus, for instance, the genus Thylacinus, re- 
presented only by the so-called Tasmanian Wolf or Thylacine, is 
now entirely restricted to Tasmania ; but the family Dasyuride, to 
which that genus belongs, ranges all over Australia, while the order 
Marsupialia, which includes the Dasyuride, is found both in Aus- 
tralia and America, and in past epochs was probably spread over 
the entire globe. ; 
A remarkable feature in connection with the distribution of the 
terrestrial Mammalia is the circumstance that, with the exception of 
certain species introduced by human agency, and small forms which 
