Baird says, that its fauna is almost identical with that of the Gila River, and has hardly any relation to that of Upper California. It possesses a considerable number (about twenty) of peculiar species of birds, but all belong to genera characteristic of the present sub-region; and there is no resemblance to the birds of Mazatlan, just across the gulf in the Neotropical region.

Reptiles, Amphibia, and Fishes.—A large number of snakes and lizards inhabit this sub-region, but they have not yet been classified with sufficient precision to enable us to make much use of them. Among lizards, Iguanidæ, Geckotidæ, Scincida, and Zonuridæ, appear to be numerous; and many new genera of doubtful value have been described. Among snakes, Calamariidæ, Colubridæ, and Crotalidæ are represented. Among Amphibia, Siredon, one of the Proteidæ, is peculiar. The rivers and lakes of the Great Central Basin, and the Colorado River, contain many peculiar forms of Cyprinidæ.

III. The Eastern or Alleghany Sub-region.

This sub-region contains examples of all that is most characteristic of Nearctic zoology. It is for the most part an undulating or mountainous forest-clad country, with a warm or temperate climate, but somewhat extreme in character, and everywhere abounding in animal and vegetable life. To the west, across the Mississippi, the country becomes more open, gradually rises, becomes much drier, and at length merges into the arid plains of the central sub-region. To the south, in Georgia, Florida, and Louisiana, a sub-tropical climate prevails, and winter is almost unknown. To the north, in Michigan and New England, the winters are very severe, and streams and lakes are frozen for months together. These different climates, however, produce little effect on the forms of animal life; the species to some extent change as we go from north to south, but the same types everywhere prevail. This portion of the United States, having been longest inhabited by Europeans, has been more thoroughly explored than other parts of North America; and to this more complete knowledge its superior zoological richness

themselves on little mounds and gaze on intruders, is noticed by all travellers. On the left, in the foreground, is one of the extraordinary pouched rats of America (Geomys bursarius). These are burrowing animals, feeding on roots; and the mouth is, as it were, double, the outer portion very wide and hairy, behind which is the small inner mouth. Its use may be to keep out the earth from the mouth while the animal is gnawing roots. A mouth so constructed is found in no other animals but in these North American rats. In the distance is a herd of bisons (Bison americanus), the typical beast of the prairies.

Birds. This sub-region has many peculiar forms of birds, both residents, and migrants from the south or north. Among the peculiar resident species we may probably reckon a dipper, (Cinclus); Salpinctes, one of the wrens; Poospiza, Calamospiza, genera of finches; Picicorvus, Gymnokitta, genera of the crow family; Centrocercus and Pediocætes, genera of grouse. As winter migrants from the north it has Leucosticte and Plectrophanes, genera of finches; Perisoreus, a genus of the crow family; Picoides, the Arctic woodpecker; and Lagopus, ptarmigan. Its summer migrants, many of which may be resident in the warmer districts, are more numerous. Such are, Oreoscoptes, a genus of thrushes; Campylorhynchus and Catherpes, wrens; Paroides, one of the tits; Phænopepla, allied to the waxwing; Embernagra and Spermophila, genera of finches; Pyrocephalus, one of the tyrant shrikes; Callipepla and Cyrtonyx, American partridges. Besides these, the more widely spread genera, Harporhynchus, Lophophanes, Carpodacus, Spizella, and Cyanocitta, are characteristic of the central district, and two genera of humming-birds-Atthis and Selasphorus-only occur here and in California. Prof. Baird notes 40 genera of birds which are represented by distinct allied species in the western, central, and eastern divisions of the United States, corresponding to our sub-regions.

It is a curious fact that the birds of this sub-region should extend across the Gulf of California, and that Cape St. Lucas, at the southern extremity of the peninsula, should be decidedly more "Central" than "Californian" in its ornithology. Prof.