vi] DISTRIBUTION OF SELECTED GROUPS 119 



from Tasmanian early Tertiary, is said to be inter- 

 mediate between Australian Poly- and Diprotodonts. 

 To sum up. Metatheria existed during the Ju- 

 rassic period both in England and in North America. 

 They disappear in Europe, but reappear in North 

 America with the Upper Cretaceous as undoubted 

 direct forerunners of marsupials, and they extended 

 their range during the same epoch into South America. 

 Opossums appeared in America in the Eocene, 

 whence they spread into Europe, but neither they, 

 nor others, flourished in the northern continents, 

 probably because the Eocene also marks the appear- 

 ance of the Placentalia, with which the inferiorly 

 organised marsupials could not compete. But that 

 marsupial stock which had got into South America 

 was safe there, because that continent we know to 

 have been separated from the north from Eocene to 

 Miocene times. There they produced a considerable 

 number of forms, until these also vanished before 

 the inroad of carnivorous Placentals, excepting the 

 opossums. Further, to the South American mar- 

 supials the way was open to the antarctic lands, 

 which in turn were connected with Australia, Ion"' 



' O 



after the latter, with Papuasia, had been severed 

 from Asia. The marsupials, after their long wander- 

 ings over three-quarters of the globe, had found in 

 the Australian region a wide expanse of country 

 in which they have developed groups analogous to 



