A similar narrow limitation occurs also among the terrestrial animals, as the family of _Colubris_ is entirely circumscribed within the boundaries of the warmer parts of the American continent. The appearance during the warmer season of the year of a few species of that family in the Northern States, does not make this case less strong. Examples might be multiplied without end to shew everywhere special adaptation, narrow circumscription, or representative adaptation of species in different parts of the world; but those mentioned will be sufficient to sustain the argument that animals are naturally antochthones wherever they are found, and have been so at all geological periods; that in northern regions they are most uniform; that their diversity goes on increasing through the temperate zone till it reaches its maximum in the tropics; that this diversity is again reduced in the aquatic animals towards the antarctic pole, though the physical difference between the southernmost extremities of America, Africa, and New Holland, seems to have called for an increased difference between their terrestrial animals. We are thus led to distinguish special provinces in the natural distribution of animals, and we may adopt the following division as the most natural: _First_, the _arctic province_, with prevailing uniformity. _Second_, the temperate zone, with at least three distinct zoological provinces--the _European temperate zone_, west of the Ural Mountains, the _Asiatic temperate zone_ east of the Ural Mountains, and the _American temperate zone_, which may be subdivided into two, the _eastern_ and the _western_--for the animals east and west of the Rocky Mountains differ sufficiently to constitute two distinct zoological provinces. Next, the tropical zone, containing the _African zoological province_, which extends over the main part of the African continent, including all the country south of the Atlas and north of the Cape Colonies; the _tropical Asiatic province_, south of the great Himalayan chain, and including the Sunda Islands, whose _Fauna_ has quite a continental character, and differs entirely from that of the Islands of the Pacific, as well as from that of New Holland; the _American tropical province_, including Central America, the West Indies, and tropical South America. _New Holland_ constitutes in itself a special province, notwithstanding the great differences of its northern and southern climate, the animals of the whole continent preserving throughout their peculiar typical character. But it were a mistake to conceive that the _Faunæ_ or natural groups of animals are to be limited according to the boundaries of the mainland. On the contrary we may trace their natural limits into the ocean, and refer to the temperate European _Fauna_ the eastern shores of the Atlantic, as we refer its western shores to the American temperate _Fauna_. Again, the eastern shores of the Pacific belong to the western