Zoological Provinces. 23 



tribution across the Atlantic. Such is also the case between 

 the fishes of Western Africa and those of Central America, 

 and between those of the southern extremities of these conti- 

 nents. The fishes of the Indian Ocean, and the fishes of the 

 Pacific vary greatly, and, though some families have a wider 

 range, there are many which are circumscribed within the 

 narrowest limits. It is one of the most striking phemonena 

 in the geographical distribution of aquatic animals, to find 

 entire families of fishes completely circumscribed within par- 

 ticular groups of islands, such, for instance, as the Za- 

 hyrinthici^ which are peculiar to the Sunda Islands, and the 

 family of Goniodonts^ which are found only in the rivers of 

 South America. 



A similar narrow limitation occurs also among the terres- 

 trial animals, as the family of Coluhris is entirely circum- 

 scribed 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. Ex- 

 amples might be multiplied without end to shew everywhere 

 special adaptation, narrow circumscription, or representative 

 adaptation of species in difiPerent parts of the world; but 

 those mentioned will be sufficient to sustain the argument 

 that animals are naturally autochthones 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 re- 

 duced in the acquatic animals towards the antarctic pole, 

 though the physical difference between the southernmost ex- 

 tremities of America, Africa, and New Holland, seems to 

 have called for an increased difference between their terres- 

 trial animals. 



We are thus led to distinguish special provinces in the 

 natural distribution of animals, and we may adopt the follow- 

 ing division as the most natural : Firsts 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 tern- 



