OF MAMMALTA. 607 
elephants, several species of rhinoceros, hippopotamus, hyzenas and lions. 
Mixed up with these in a remarkable manner are the remains of 
northern forms like the wolverene, arctic fox, northern vole and reindeer, 
From this it follows that the past history ofthe Holarctic region is to 
a large extent an epitome ofthe faunas found in the other several regions 
(leaving out of consideration the Sonoran). In early Oligocene of Europe 
we find the lemurs and civets, now so characteristic of the Madagascar 
region, and later on in the Pliocene and Pleistocene, the fauna with its 
early aard-varks, elephants, hippopotamuses, and other early ungulates 
approximated to the present-day fauna of Ethiopia and to the present 
and early past of the Oriental. As most of those occur in the Miocene of 
India, it is probable that they migrated thence to Europe, either directly 
or through northern Africa. 
The resemblances in the faunas of North America and northern 
Eurasia are usually explained as being due to a land-connection across 
Behring sea, for which there is muchevidence. Thisserved to cause an 
approximation in faunas between the northern parts, leaving the Sonoran 
ah and the Medissarenea district more or less distinct from each 
other 
5. Sonoran ReEcion.—This, comprising practically the 
United States of America, has been constituted as a separate 
region mainly because it is a transition zone between Hol- 
arctic and Neogcea, though it has some peculiar types of 
its own. Of Neogcean types, we may note the armadillos, 
opossums, peccaries and some Procyonide, whilst the skunks 
and other Mustelide, the marmots and the pouched rats, 
form Holarctic types. The most typital family of the 
region is the American prongbuck (Azflocapra) which 
has deciduous horns. This species also extends partly 
into Canada. 
We may add here the names of some of the most char- 
acteristic mammals found at the present day in the regions 
of Arctogcea :— 
[TABLE. 
