SECTION II.

DISTRIBUTION OF THE FAUNAS

413. We have stated that all the faunas of the globe may be divided into three groups, corresponding to as many great climatal divisions, namely, the glacial or arctic, the temperate and the tropical faunas. These three divisions appertain to both hemispheres, as we recede from the equator towards the north or south poles. It will hereafter be shown that the ropical and temperate faunas may be again divided into several zoological provinces, depending on longitude or on the peculiar configuration of the continents.

414. No continent is better calculated to give a correct idea of distribution into faunas, as determined by climate, than the continent of America; extending as it does across both hemispheres, and embracing all latitudes, so that all climates are represented upon it, as shown by the chart on the following page.

415. Let a traveller embark at Iceland, which is situated on the borders of the polar circle, with a view to observe, in a zoological aspect, the principal points along the eastern shore of America. The result of his observation will be very much as follows. Along the coast of Greenland and Iceland, and also along Baffin's Bay, he will meet with an unvaried fauna, composed throughout of the same animals, which are also for the most part identical with those of the arctic shores of Europe. It will be nearly the same along the coast of Labrador.

416. As he approaches Newfoundland, he will see the landscape, and with it the fauna, assuming a somewhat more varied aspect. To the wide and naked or turfy plains of the boreal regions succeed forests, in which he will find

various animals which dwell only in forests. Here the tem perate fauna commences. Still the number of species is not yet very considerable; but as he advances southward, along the coasts of Nova Scotia and New England, he finds new species gradually introduced, while those of the colder regions diminish, and at length entirely disappear, some few accidental or periodical visiters excepted, who wander, during winter, as far south as the Carolinas.

417. But it is after having passed the boundaries of the United States, among the Antilles, and more especially on the southern continent, along the shores of the Orinoco and the Amazon, that our traveller will be forcibly struck with the astonishing variety of the animals which people the forests, the prairies, the rivers, and the sea-shores, most of which he will also find to be different from those of the northern continent. By this extraordinary richness of new forms, he will become sensible that he is now in the domain of the tropical fauna.

418. Let him still travel on beyond the equator towards the tropic of Capricorn, and he will again find the scene change as he enters the regions where the sun casts his rays more obliquely, and where the contrast of the seasons is more marked. The vegetation will be less luxuriant; the palms will have disappeared to make place for other trees; the animals will be less varied, and the whole picture will recall to him, in some measure, what he witnessed in the United States. He will again find himself in the temperate region, and this he will trace on, till he arrives at the extremity of the continent, the fauna and the flora becoming more and more impoverished as he approaches Cape Horn.

419. Finally, we know that there is a continent around the South Pole. Although we have as yet but very imperfect notions respecting the animals of this inhospitable clime, still, the few which have already been observed there present

a close analogy to those of the arctic region. It is another glacial fauna, namely, the antarctic. Having thus sketched the general divisions of the faunas, it remains to point out the principal features of each of them.

420. I. ARCTIC FAUNA. The predominant feature of the Arctic Fauna is its uniformity. The species are few in number; but, on the other hand, the number of individuals is Immense. We need only refer to the clouds of birds which hover upon the islands and shores of the North; the shoals of fishes, the salmon among others, which throng the coasts of Greenland, Iceland, and Hudson's Bay. There is great uniformity, also, in the form and color of these animals. Not a single bird of brilliant plumage is found, and few fishes with varied hues. Their forms are regular, and their tints as dusky as the northern heavens. The most conspicuous animals are the white-bear, the moose, the reindeer, the musk-ox, the white-fox, the polar-hare, the lemming, and various Seals; but the most important are the Whales, which, it is to be remarked, rank lowest of all the Mammals. Among the Birds may be enumerated some sea-eagles and a few Waders, while the great majority are aquatic species, such as gulls, cormorants, divers, petrels, ducks, geese, gannets, &c., all belonging to the lowest orders of Birds. Reptiles are altogether wanting. The Articulata are represented by numerous marine worms, and by minute crustaceans of the orders Isopoda and Amphipoda. Insects are rare, and of inferior types. Of the type of Mollusks, there are Acephala, particularly Tunicata, fewer Gasteropods, and very few Cephalopods. Among the Radiata are a great number of jelly-fishes, particularly the Beröe; and to conclude with the Echinoderms, there are several star-fishes and Echini, but few Holothuriæ. The class of Polypi is very scantily represented, and those producing stony corals are entirely wan ing.

421. This assemblage of animals is evidently inferior t♪ that of other faunas, especially to those of the tropics. Not that there is a deficiency of animal life; for if the species are less numerɔus, there is a compensation in the multitude of individuals, and, also, in this other very significant fact, that the largest of all animals, the whales, belong to this fauna.

422. It has already been said, (400,) that the arctic fauna of the three continents is the same; its southern limit, however, is not a regular line. It does not correspond precisely with the polar circle, but rather to the isothermal zero; that is, the line where the average temperature of the year is at 32° of Fahrenheit. The course of this line presents numerous undulations. In general, it may be said to coincide with the northern limit of trees, so that it terminates where forest vegetation succeeds the vast arid plains, the barrens of North America, or the tundras of the Samoyedes. The uniformity of these plains involves a corresponding uniformity of plants and animals. On the North American continent it extends much farther southward on the eastern shore than on the western. From the peninsula of Alashka, it bends northwards towards the Mackenzie, then descends again towards the Bear Lake, and comes down nearly to the northern shore of Newfoundland.

423. II. TEMPERATE FAUNAs. The faunas of the temperate regions of the northern hemisphere are much more varied than that of the arctic zone. Instead of consisting mainly of aquatic tribes, we have a considerable number of terrestrial animals, of graceful form, animated appearance, and varied colors, though less brilliant than those found in tropical regions. Those parts of the country covered with forests especially swarm with insects, which become the food of other animals; worms and terrestrial and fluviatile mol. lusks are also abundant.