GENERAL LAWS OF DISTRIBUTION. 191 



not overstep. The Condor of the Cordilleras does not de- 

 scend 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 some- 

 times 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 faunas, still, marked differences between the 

 animals of great basins are not less observable. Properly 

 to apprehend 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 



O ' O 



on soundings. 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 run along the 

 shores. The range of marine species being, therefore, con- 

 fined to the vicinity of the shores, their distribution must be 

 subjected to laws similar to those which regulate the terres- 

 trial 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 



