MARINE DISTRIBUTION. 69 



currence of purely pelagic animals. On the other hand, shal- 

 low-water marine animals fall into assemblages characteristic 

 of definite areas or provinces of distribution — that is to say, 

 though many species have a world-wide distribution, others 

 occur only in particular localities, and certain geographical 

 areas are marked by the existence in them of a number of 

 such peculiar species. The basins of the Pacific, the Indian 

 Ocean, the Atlantic, the Mediterranean, and the Arctic seas, 

 are thus especially characterized ; and even limited areas of 

 these great geographical divisions, such as the Celtic, the 

 Lusitanian, and the Australian, have their peculiar features. 



But, though the shallow-water marine faunas thus follow 

 the broad features of physical geography, and though, within 

 each great province of distribution thus marked out, temper- 

 ature and other physical conditions have an obvious influence 

 in determining the range of species ; yet, on comparing any 

 two great areas together, differences in climatal conditions 

 are at once seen to be inadequate to account for the differ- 

 ences between the faunas of the two areas. Climate in no 

 way enables us to understand why the Trigonia, the pearly 

 Nautilus, the Cestracion, the eared seals, and the penguins, 

 are found in the Pacific and not in the Atlantic area ; 1 nor 

 why the Cetacea of the arctic and antarctic regions should be 

 as different as they are. When we turn to the distribution 

 of land-animals, the boundaries of the provinces of distribu- 

 tion correspond neither with physical features nor with cli- 

 matic conditions. Mammals, birds, reptiles, and amphibians, 

 are so distributed at the present da}' as to mark out four great 

 areas or provinces of distribution of very unequal extent, in 

 each of which a number of characteristic types, not found 

 elsewhere, occur. These are : 1. The Arctogceal, including 

 North America, Europe, Africa, and Asia as far as Wallace's 

 line, or the boundary between the Indian and the Papuan 

 divisions of the Indian Archipelago ; 2. The Austrocolum- 

 bian, comprising all the American Continent south of Mexico; 

 3. The Australian, from Wallace's line to Tasmania ; 4. The 

 Novozelanian^ including the islands of New Zealand. 2 



1 Penguins are found at the Cape of Good Hope and at the Falkland Islands, 

 hut not in the northern pails of the west coast of Africa, nor of the east coast 

 of South America. In the Pacific they stretch north to the Papuan and Peru- 

 vian coasts. 



2 On the classification and distribution of the Alectoromorphce and Hetero- 

 morphce : Proceedings of the Zoological Society, 1868. Sclater on the " Geo- 

 graphical Distribution of Birds," Ibid., vol. ii. Pucheran, " Kevue et Magasin 

 cle Zoologie," 1865. Murray, " The Geographical Distribution of Mammals." 



