GENERAL LAWS OF DISTRIBUTION. 159 



they do not overpass. The Condor of the Cordilleras does 

 not descend into the temperate regions of the United States ; 

 and yet it is not that he fears the cold, since he is frequently 

 known to ascend even above the highest summits of the 

 Andes, and disappears from view where the cold is most 

 intense. Nor can it be from lack of prey. 



407. Again, the peculiar configuration of a country 

 sometimes determines a peculiar grouping of animals, into 

 what may be called local faunas. Such, for example, are 

 the prairies of the West, the Pampas of South America, the 

 Steppes of Asia, the Deserts of Africa ; and for marine 

 animals, the basin of the Caspian. In all these localities, 

 animals are met with which exist only there, and are not 

 found except under those particular conditions. 



408. Finally, to obtain a true picture of the zoological 

 distribution of animals, not the terrestrial types alone, but 

 the marine species must also be included. Notwithstanding 

 the uniform nature of the watery element, the animals which 

 dwell in it are not dispersed at random ; and though the 

 limits of the marine may be less easily defined than those of 

 the terrestrial fauna, still, marked differences of the animals 

 in the great basins are not less observable. Properly to ap- 

 prehend how marine animals may be distributed into local 

 faunas, it must be remembered that their residence is not in 

 the high sea, but along the coasts of continents and on sound- 

 ings. It is on the Banks of Newfoundland, and not in the 

 deep sea, that the great cod-fishery is carried on ; and it is 

 well known that when fishes migrate, they take care to run 

 along the shores. The range of marine species being there- 

 fore confined to the vicinity of the shores, their distribution 

 must be subjected to laws similar to those which regulate the 

 terrestrial faunas. As to the fresh-water fishes, not only do 

 the species vary in the different zones, but even the different 

 rivers of the same region have species peculiar to them, and 

 not found in neighboring streams. 



