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 

 Kegiou, 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 distribution throughout the realm 30 



Peculiar to the African Eegion 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 Eegion, 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 " Palseotropical" — 

 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. 



