Geograpliical Distribution of Animals. 209 



Zoological Provinces, 



8. The geograpliical coincidence, more or less exact, of many 

 specific areas constitutes a zoological province. 



9. Zoological Provinces, except those which are insular, are 

 for the most part three or four thousand miles in diameter. 



10. The fact that one fauna extends through all longitudes 

 in the Arctic regions is not an isolated fact, as has been 

 supposed. It results from the diminution of the degrees of 

 longitude, so that the Arctic zoological province extends 

 through all longitudes, merely because it has the ordinary 

 dimensions of a zoological province. On the other hand, the 

 three great southern points of land, Patagonia, South Africa, 

 and New Holland, are too remote from each other to be 

 comprised in one zoological marine province.* But it may be 

 predicted, that only one zoological province will be found 

 in the Antarctic zone. 



11. The difference of aquatic, terresirial, and aerial habits has 

 the most important connexion with geographical distribution. 

 Next in importance is climate. Next, and of much less impor- 

 tance, is zoological affinity. The influence of zoological affinity 

 is seen in the fact that the area o^ one group of species sometimes 

 does not coincide with that of another group, of the same habits 

 in respect of climate and station ; as the Melanidoe and Limniadaa 

 of the United States. The same species of Limniada; extend 

 through the Western, Middle, and Eastern States, but the 

 Melanida3 do not enter any of the Eastern States. Their 

 eastern boundary is therefore four to five hundred miles west of 

 the eastern boundary of the Limniada?. 



12. The figure of a zoological province depends chiefly on 

 the distribution of land and water in connexion with lati- 

 tude. 



13. Several distinct insular terrestrial zoological provinces 



* The separation by water, irrespective of great distance, would alone give 

 them distinct terrestrial faumc 



