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by the northern branch of the Saskatchewan, and ends on the Pacific coast in the neighbourhood of Queen Charlotte's Sound. But long prolongations of this Sub-region extend down the Alleghany mountains; in the east as far as Georgia, along the Rocky Mountains as far as the Rio Grande, and along the Cascade and Sierra Nevada mountains as far as the Colorado river. Besides these, there are several smaller detached portions of other mountain ranges, which should be attributed to the Canadian Subregion.
The Eastern or "Humid" Sub-region is separated from the Western or “Arid" by a line running roughly nearly along the meridian of 100° west of Greenwich, and extending from Manitoba to the mouth of the Rio Grande del Norte.
SECTION IV.-THE CANADIAN OR COLD SUB-REGION
The Canadian Sub-region is especially remarkable for a number of genera which are common to it and the northern part of the Old World, but which do not extend southwards into the other Sub-regions to be presently treated of. It is further characterized by the small number of genera which are essentially New World forms, and have no connection with the Old World. Reviewing the Mammals in detail, we find that the Sub-region contains no representative of either Marsupials or Edentates. On the other hand, there are six genera of the Ungulates within its limits a far larger proportion than that found in the other Sub-regions. Of these the only one endemic is Haploceros (the Rocky Mountain goat). This somewhat isolated Ruminant has its nearest allies in the genus
Nemorhædus, of the mountains of Asia, which occurs in Japan (N. crispus), but of which the best-known form is commonly designated the "Serow" by the sportsmen of the Himalayas. There are also no less than four genera found in the Old World, and also in the Canadian Subregion, which do not extend further south. These are Cervus, containing the Wapiti (C. canadensis), closely allied to the Red Deer of the Old World; the Cariboo (Rangifer), which cannot be distinguished from the Reindeer of the northern part of the Palearctic Region: and the Moose (Alces machlis), which has the same distribution as the Reindeer, but is known in Europe under the name of "Elk." Besides these, there are two Canadian genera of this order which are found in other Sub-regions as well as in the Old World, namely, the Bison (Bison) and the Sheep (Ovis). The Bison, of which the American representative is the socalled buffalo (now, alas! nearly extinct), is closely allied to the European Bison, still found in certain parts of the Old World; while the Big-horn Sheep (Ovis canadensis) is a representative of the Wild Sheep, which are extensively distributed in the Palearctic Region. The number of genera of Rodents of the Canadian Sub-region amounts in all to eighteen, of which three are peculiar. One of these is Haplodon, to which allusion has already been made; the others are Phenacomys, a small genus of rats, and Erethizon, which contains only the Tree-porcupine of the Canadian forests. Among the members of this order, too, we find three genera common to this Sub-region and the Old World, which do not extend further south. These are Myodes (M. obesus), which is represented in Europe by an allied species, the well-known Lemming of Scandinavia ; Cuniculus, a form nearly allied to the Lemming; and
Lagomys, the "Pika," or Tailless Hare, which is found in the higher mountain ranges of both the Old and the New Worlds.
The Carnivora do not present many features of special interest. Two genera-Mustela, containing the Weasels, and Gulo, the Glutton, have much the same circumpolar distribution as has been already remarked on in the case of the Deer and the Lemming.
The number of genera of Insectivora and Chiroptera in the Canadian Sub-region is insignificant, and they are of no interest from a distributional point of view.
Viewing the fauna of the Canadian Sub-region as a whole, it will thus be seen that its greatest point of interest is its resemblance to that of the more northerly parts of the Old World. This, of course, may be easily accounted for when we recollect that the sea of Behring Straits is quite shallow, and in places not more than about 20 miles in breadth. There can be no doubt that there was a landconnection between Siberia and Alaska in comparatively recent geological times, and that this has resulted in the commingling of the faunas of the northern parts of these two Regions, to a considerable extent. This land-bridge must have existed so recently that there has not yet been even time for, in some cases, the animals to become differentiated into appreciable species, as in the cases, for example, of the reindeer and elk.
Below will be found a summary of the genera of the Canadian Sub-region, forty in number, which are divided into five categories much in the same fashion as has been done in the previous articles, namely:
1. Endemic-those found only in the Canadian Subregion.
2. Nearctic-those not found beyond the limits of the Nearctic Region.
3. Neogean-those found in the New, but not in the Old World.
4. Arctic and Palæogean-those which are found in the Old World, and only in the Canadian Sub-region of the New; and, finally
5. Neogean and Palæogean-containing the most widely distributed forms.
SECTION V.-THE WESTERN OR ARID SUB-REGION
This Sub-region is, on the whole, the richest of the three, both as regards the total number of genera found within its limits and also as regards the number of genera peculiar to it, which amounts to seven out of fifty-three, as compared with four out of forty in the Canadian, and one out of forty in the Eastern.
The Western Sub-region shares with the Eastern the only representative of the Marsupials found in North America, the Virginian Opossum. Just extending, too, to within its limits occurs the only member of the Order
Edentata, the Nine-banded Armadillo (Tatusia novemcincta). Among the Ungulates, the Prong-buck (Antilocapra) is restricted to this Sub-region, and the genus Cervus of the cold Temperate Sub-region is replaced by the purely American genus Cariacus, of which the Black-tailed Deer is the representative.
This Sub-region is also more particularly the home of the American Bison, which, however, ranged even in historic times eastward nearly to the Atlantic seaboard. Among the Rodents there are no less than five endemic genera, of which, perhaps, the best known is Cynomys, the Prairiedog. The other endemic genera all belong to the family Geomyida, which contains a number of small Rodents known as Pocket-gophers.
Among the Carnivora there are no genera in the Western Sub-region which are not more or less widely distributed, the greater number of them, both in the case of this order and of the last, being also found in the Old World. Three genera of Moles belonging to the next order, Insectivora, though confined to North America, extend into the Eastern Sub-region. The Bats of the Arid Sub-region include among their members two genera (each with one species) which occur only in California, while four other genera are found only in the New World. One of these, Macrotus, is of special interest, since it contains the only member of a very large and well-marked family (Phyllostomatida), which extends into the Nearctic. Region from South America.
This Sub-region, as compared with the Canadian, contains a far larger proportion of Neotropical genera, and, in addition, is characterized by the absence of a number of the Palearctic forms found only in the Canadian Sub-region.