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

7;chap, iv.] ZOOLOGICAL REGIONS. 73Ethiopian Region.—The limits of this region have been indicatedby the definition of the Palsearctic region.Besides Africasouth of the tropic of Cancer, and its islands, it comprises thesouthern half of Arabia.This region has been said to be identical in the main charactersof its mammalian fauna with the Oriental region, and hastherefore been united with it by Mr. A. Murray. Most importantdifferences have however been overlooked, as the followingsummary of the peculiarities of the Ethiopian region will, Ithink, show.It possesses 22 peculiar families of vertebrates ; 90 peculiargenera of mammalia, being two-thirds of its whole numberand 179 peculiar genera of birds, being three-fifths of all itpossesses. It is further characterized by the absence of severalfamilies and genera which range over the whole northernhemisphere, details of which will be found in the chaptertreating of the region. There are, it is true, many pointsof resemblance, not to be wondered at between two tropicalregionsin the same hemisphere, and which have evidently beenat one time more nearly connected, both by intervening landsand by a different condition of the lands that even now connectthem.remarkable ;But these resemblances only render the differences moresince they show that there has been an ancient andlong-continued separation of the two regions, developing a distinctfauna in each, and establishing marked specialitieswhichthe temporary intercommunication and immigration has notsufficed to remove. The entire absence of such wide-spreadgroups as bears and deer, from a country many parts of whichare well adapted to them, and in close proximity to regionswhere they abound, would alone mark out the Ethiopian regionas one of the primary divisions of the earth, even if it possesseda less number than it actually does of peculiar family andgenericgroups.Sub-divisions of the Ethiopian Region.—The African continentsouth of the tropic of Cancer is more homogeneous in itsprominent and superficial zoological features than most of theother regions, but there are nevertheless important and deep-Vol. I.—