TERTIARY MAMMAL HORIZONS. 57 



fauna but not in connection with its antecedent cause. This 

 cause I believe to have been mainly an invasion from south to 

 north correlated with the northern extension of Ethiopian cli- 

 mate and flora during the Middle Tertiaiy. It is in a less meas- 

 ure due to a migration from north to south. Let us therefore 

 clearly set forth the hypothesis of tlic Ethiopian region or South 

 Africa as a great center of independent evolution and as the 

 source of successive northward migrations of animals, some of 

 which ultimately reached even the extremity of South America — 

 I refer to the Mastodons. This hypothesis is clearly implied if 

 not stated by Blanford in 1876 in his paper upon the African 

 element in the fauna of India. 



The first of these migrations we may suppose brought in cer- 

 tain highly specialized ruminants of the upper Eocene, the 

 anomalures or peculiar flying rodents of Africa ; with this in- 

 v^asion may have come the pangolins and aard varks, and 

 possibly certain armadillos, Dasypodidcr, if M. Filhol's identi- 

 fication of Necrodasypiis is correct. A second invasion of great 

 distinctness may be that which marks the beginning of the 

 Miocene when the mastodons and dinotheres first appear in 

 Europe, also the earliest of the antelopes. A third invasion 

 may be represented in the base of the Pliocene by the increasing 

 number of antelopes, the great giraffes of the ^-Egean plateau, 

 and in the upper Pliocene by the hippopotami. With these 

 forms came the rhinoceroses with no incisor or cutting teeth, 

 similar to the smaller African rhinoceros, R. bicornis. An- 

 other recently discovered x^frican immigrant upon the Island of 

 Samos in the ^Egean plateau is Pliohyrax or Leptodon, a very 

 large member of the Hyracoidea, probably aquatic in its habits, 

 indicating that this order enjoyed an extensive adaptive radiation 

 in Tertiary times. 



It thus appears that the Proboscidia, Hyracoidea, certain 

 edentata, the antelopes, the giraffes, the hippopotami, the most 

 specialized ruminants, and among the rodents, the anomalures, 

 dormice, and jerboas, among monkeys the baboons, may all 

 have enjoyed their original adaptative radiation in Africa ; that 

 they survived after the glacial period, only in the Oriental 



