The geographical distribution of animals, with a study of the relations ...

;chap. iv.] ZOOLOGICAL REGIONS. 65We see, then, that even the exceedingly rich and isolated Neotropicalregion is less rich and diversified in its forms of mammalianlife than the very much smaller area of the Indian region,or the temperate Palcearctic, and very much less so than theEthiopian region ; while even the comparatively poor Nearcticregion, is nearly equal to it in the number of its family types. Ifthese were united they would possess fifty-five families, a numbervery disproportionate to those of the remaining two.Anotherconsideration is, that although the absence of certain forms oflife makes a region more isolated, it does not make itzoologicallymore important ; for we have only to suppose some five or sixfamilies, now common to both, to become extinct either in theEthiopian or the Indian regions, and they would become asstrongly differentiatedwhile still remaining as rich in family types.from all other regions as South America,In birds exactly thesame phenomenon recurs, the family types being less numerous inSouth America than in either of the other tropical regions of theearth, but a larger proportion of them are restricted to it.It willbe shown further on, that the Ethiopian and Indian, (or, as I proposeto call it in this work, Oriental) regions, are sufficiently differentiatedby very important groups of animals peculiar toeachand that, on strict zoological principles they are entitled torank asregions of equal value with the Neotropical and Australian.It is perhaps less clear whether the Palsearctic shouldbe separated from the Oriental region, with which it has undoubtedlymuch in common ; but there are many and powerfulreasons for keeping it distinct.facies in the animal forms of the two regions ;There is an unmistakably differentand although nofamilies of mammalia or birds, and not many genera, are whollyconfined to the Palsearctic region, a very considerable numberof both have their metropolis in it,and are very richly represented.The distinction between the characteristic forms of life in tropicaland cold countries is,on the whole, very strongly marked in thenorthern hemisphere ; and to refuse to recognise this in a subdivisionof the earth which is established for the very purpose ofexpressing such contrasts more clearly and concisely than byordinary geographicalterminology, would be both illogical and