Page:Encyclopædia Britannica, Ninth Edition, v. 7.djvu/293

ANIMAL.] DISTRIBUTION 275 Cha/maxi, forming a distinct family allied to the wrens, is the most interesting and peculiar bird. The central or Eocky Mountain suit-region extends eastward from the Sierra Nevada across the Rocky Mountains to a line a little eastward of the 100th meridian, where a marked change in the cli mate, vegetation, and animal life is found to occur. To the north it is bounded by the great Canadian forest-zone on the upper Sas katchewan, while southwards it extends into Texas and Lower California and along the line of highlands to beyond _the city of Mexico. This sub-region is characterized by many peculiar animals, some of which are closely allied to Palrcarctic types as the so-called buffalo (Bison ainericanus), the big-horned sheep (Om montana), the glutton (Gulo arcticus), and thepika (Lagomys princeps] ; while others are altogether distinct forms, as the prong -horn (Ant.ilo- cnpra) and the antelope or mountain goat (Aplocerus). Of False- arctic forms of birds it has two peculiar genera of grouse (Centra- cercus and Pediocetes), and the Arctic wood-pecker and ptarmigan. More especially Nearctic are a genus of wrens (Salpinctes) and some peculiar genera of finches and crows. The Nearctic pouched- rats (tiaccomyulce) are abundant. The eastern or Alleghany sub-region comprises the country to the east of the last, and as "far north as Wisconsin and the southern parts of Canada, It contains examples of all that is most charac teristic in Nearctic zoology, and has besides a few peculiar groups. Of these the most noteworthy is the star-nosed mole (Condylura), and among birds the passenger-pigeon ( Ectopistes) and a few groups of wood-warblers and finches. The reptiles are more peculiar, as there are several genera of snakes, including two of Homalopsidtc and two of rattle-snakes, which hardly extend beyond it. Among lizards the glass-snake (OphisauruS) is peculiar, and no less than four genera of tortoises are almost or quite confined to the sub- region. Here, too, are found the peculiar Amphibia for which North America is so remarkable, such as the two genera of the Sirenidffi (Siren and Pscudobranchus), Menobranchus allied to the Proteus of Europe, Amphiuina, an. eel-like creature with four rudimentary feet constituting a distinct family, and three peculiar genera of salamanders (Salamandridce). Fishes, too, are very abundant, and several of the peculiar North American forms are confined to this sub-region ; such are the pirate-perch (Aphredo- derus), the cave-fishes (Amblyopsidce}, the trout-perches (Per- copsidoe), several genera of sun-fishes (Ichthclidce), and many others The sub-Arctic or Canadian sub-region has very few distinctive features, but it serves at once to connect and separate the other three regions which almost merge into it. The musk-sheep (Ovibos) is almost the only form peculiar to it, though this is more pro perly Arctic. Many of the most characteristic Nearctic animals, such as Condylura and Mephitis, only just enter its southern bor ders, while most of the Arctic forms are more abundant here than further south. Great numbers of birds migrate here in summer from the Southern States and Mexico; while a few especially Palaearctic groups (as Budytes, Phylloscopus, and Pijrrhiila), which do not occur elsewhere in North America, have been found in Alaska. The scanty fauna of Greenland shows that it forms a part of this sub-region. DISTRIBUTION OF THE HIGHER ANIMALS DURING THE TERTIARY PERIOD. Before we proceed to other divisions of our sub ject, we shall find it useful to consider briefly the geo graphical relations of the Tertiary and post-Tertiary faunas to that which now exists, as we shall thereby arrive at a better comprehension of the true nature of zoological regions, and the meaning of the diverse and complex rela tions that exist between them. Post-Tertiary Faunas. Researches in alluvial clays and gravels, cave-earths, and other superficial deposits have made known to us very completely the character of the fauna which immediately preceded that now existing, and which lived at the close of the glacial period and in the era of prehistoric man. We find, as might be expected, that a considerable number of the Mammalia were identical with living species, but along with these we almost always find a number of extinct forms, some closely related to living species in the same district, while others seem to indicate migration and a change of climate, by their resemblance to species which now only live further north or south. More extraordinary is the fact, that many of these recently extinct forms were of huge size as compared to any now living, often reminding us of the bulkiest in habitants of the tropics or of those huge animals which we associate with an earlier condition of the earth s surface. Thus, in Europe during the post-Tertiary period, the reindeer, the glutton, and the Tartarian antelope inhabited France, along with powerful felines allied to the existing lion. At the same time elephants and rhinoceroses of several species roamed all over Europe ; and at one period hippopotami ranged as far north as the Thames, while the European beaver was replaced by a much larger species. In North America about the same time we find extinct lions, horses, tapirs, and camels, with bisons and musk- sheep, as well as elephants and mastodons ; and along with these, three genera of gigantic sloths as large as rhinoceroses and elephants, forming an assemblage of large Mammalia wonderfully different from that which now exists in the same country. In South America we find that there were larger monkeys than any now living, together with lions, bears, horses, tapirs, and antelopes, as well as mastodons, and a tree-porcupine as large as a peccary. Here also were armadillos as large as a rhinoceros, and huge sloths as in North America but of more varied kinds. Even in Australia very similar phenomena occur. Extinct wombats as large as tapirs, kangaroos the size of elephants, and a phalanger nearly as large as a lion have been found in cave-deposits, along with a number of other forms more nearly like those now living. But in this case all are Marsupials or Monotremes, and there is no sign of any migration from other lands, which indeed, owing to the insular nature of the country, we could hardly expect. Again, in New Zealand and Madagascar we have a similar phenomenon presented to us by the great extinct terrestrial birds the " moas," the " dodos," and the Epyornis, which, from the conditions under which their remains are found, have evidently not long ceased to exist. It appears then that in all parts of the world where we have been able to obtain the requisite information, the period which immediately preceded that in which we live was characterized by great movements or migrations of the higher animals where that was possible ; and everywhere, by the extinction of a variety of huge animals belonging to almost every order of Mammalia and to several orders of birds, many of which are now totally unrepresented on the globe. Tertiary Faunas, and their Geographical Relations with those of the six Zoological Regions. When we go back to the late and middle Tertiary deposits, we find a series of remains of the higher animals which exhibit yet more remarkable changes of distribution. Various parts of cen tral and southern Europe, for example, were then inhabited by animals which now form the most characteristic features of Ethiopian and Oriental zoology such as apes and monkeys, lions and hytenas, horses, tapirs, elephants, rhinoceroses, giraffes, and various antelopes ; and along with these a number of extinct ancestral forms of many of the same groups. Among birds, too, we find the eastern jungle-fowl, the edible-nest swift, and the trogon, along with African parrots and plantain-eaters. In the Miocene beds of Northern India are found such typical African groups as the hippopotamus and giraffe. Now geology teaches us, that in the Eocene, or earliest portion of the Tertiary epoch, a continuous arm of the soa extended from the Bay of Bengal to the Atlantic Ocean, cutting off the peninsula of India and Central Africa from the Paloearctic region ; x and it is therefore highly probable that, when this sea-bed became dry land, the various laro-e Mammalia now so characteristic of Africa entered it for the 1 See Mr Searles V. "Wood, jun., " On the Form and Distribution of the Land Tracts during the Secondary and Tertiary Periods re spective!} , and on the effect upon Animal Life which great changes in Geographical Configuration have probably produced " (Philosophical

Magazine, 1862).