« AnteriorContinuar »
American mammals, first of all excludes from what he terms the North American Region the extreme northern parts of that continent. He considers that the Arctic portion of that continent, namely, that beyond the limit of arboreal vegetation, forms, together with the similar part of the Old World, a separate Region, or, as he terms it, "the Arctic Realm."
Furthermore, the southern part of North America south of the Mexican tableland, together with the lowlying country of Mexico on either flank, he assigns to the American Tropical Realm. The remainder of the continent, combined with the great mass of Europe and Asia, forms, according to this author, the North Temperate Realm. This scheme of division does not differ essentially from that of Mr. Allen. The Arctic portion of North America forms, no doubt, as Mr. Allen puts it, “part of a homogeneous hyperborean faunal area of circumpolar distribution."
Mr. Allen's American Tropical Realm has already been treated of in the chapter of this volume dealing with the Neotropical Region (see p. 52). There remains, therefore, Mr. Allen's North American Region, which nearly corresponds to the Nearctic Region of our scheme of classification. Mr. Allen divides his North American Region into two Subregions—the Cold Temperate and the Warm Temperate, the two latter falling into two provinces, a Humid or Eastern and an Arid or Western. Proceeding further, he divides the Humid province into two sub-provinces, namely, an Apalachian or Northern and an Austro-riparian or Southern. The Arid or Western province is also separated into two sub-provinces—the Campestrian or Northern and the Sonoran or Southern, and, besides this, the sub
provinces are divided into various minor divisions termed districts and faunas.
It will be sufficient for our present purpose to divide the North American or Nearctic Region into three Subregions; these may be termed, (1) the Canadian or Cold Sub-region, (2) the Western or Humid Sub-region, and (3) the Eastern or Arid Sub-region.
Mr. Wallace has recognized four Sub-regions in the Nearctic Region. His Canadian Sub-region corresponds fairly well to the Canadian or North Temperate of Mr. Allen, except for the fact that it has not been made by Mr. Wallace to extend southward down the mountain ranges. The Alleghany Sub-region of Mr. Wallace, again, practically corresponds to the “Humid” of Mr. Allen. The two others, the Rocky Mountain and Californian, correspond to Mr. Allen's “ Arid,” the Californian Sub-region being composed of a narrow strip of coast country between the Sierra Nevada and the sea, and extending from Queen Charlotte's Sound in the north to the south-western corner of California. The differences, therefore, between Mr. Wallace's and Mr. Allen's views are not so fundamental as one would gather from the critical remarks of the latter author.
The boundaries of the Sub-regions here adopted will be best understood by reference to the accompanying map (Plate VI., p. 176).
The Canadian or Cold Sub-region embraces the whole of the northern portion of North America, including Greenland. The southern limit of this Sub-region commences, on the Atlantic side, on the coast of Maine, in the neighbourhood of Augusta, and thence runs to Quebec and through the Great Lakes. Further west it is bounded 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 pf 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 Palæarctic 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 inust 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.