352 



BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



the northern hemisphere. Thus the African Eegion is the more special- 

 ized division, only a small portion of the tropical element in the Indian 

 Eegion, through which it is differentiated from the great Europseo- 

 Asiatic Temperate Eegion, being unrepresented in the African, while the 

 African has three times as many peculiar families as the Indian.* As 

 shown by the subjoined table, thirty of the fifty Indo-African families 

 have a wide extralimital distribution, not less than one-fourth being 

 emphatically cosmopolitan. 



Families of Mammals represented in the Indo-African Realm, arranged to show (approxi- 

 mately) their distribution. 



Summary. 



Whole number 50 



Of general distributiqn throughout the realm 30 



Peculiar to the African Region ..". 10 



Peculiar to the Indian Region 3 



Occurring in the Indian Region, but not in the African ., 6 



Of wide extralimital range 16 



African Eegion. The African Eegion, as here recognized, is nearly 

 equivalent to Mr. Wallace's "Ethiopian Eegion ", with the exclusion 



* Mr. Wallace has arrived at rather different conclusions respecting the specializa- 

 tion of the African Region, since he considers its specialization due wholly to the 

 peculiar forms developed in Madagascar. Deducting these for he considers Madagascar 

 and its neighboring islands as forming a "subregion"merely of the " Palaeotropical" 

 he believes would leave, in respect to specialization, the African and Indian Regions 

 "nearly equal". In this comparison, however, I wholly exclude the Madagascan or 

 " Lemurian" fauna, and still find Africa a considerably more specialized region. 



