452 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1912. 



Whereas New Zealand in its relation with South America, via 

 Antarctica, appears both as a giver and a receiver, Australia, on 

 the contrary, seems to have made no return to South America, but 

 to have received all and given nothing.^ No Eucalypts, for instance, 

 crossed from Tasmania to Patagonia. One explanation may be that 

 Australia was then too poor to afford emigrants. Another and 

 more probable explanation is that Antarctica, having received a 

 fauna and flora from Archiplata, was severed from it before joining 

 Australia. Thus a stream of migration would be forced forward and 

 checked backwards. 



The austral fauna and flora appears extending in successive zones 

 from the far south to the Tropics. In New Zealand the warmth- 

 loving plants and animals, such as the Kauri pine (a relation of 

 Araucaripi) and Placostylus snail, have been thrust to a northern 

 refuge, while diminished temperature has probably exterminated 

 others. The Araucaria and iguanas, the fresh-water fish Osteoglossum, 

 are examples of tropical austral forms of which a long list could be 

 compiled. 



It is unlikely that the Antarctica that bore this tropical and 

 subtropical assembly reached much more broadly to the Tropics 

 than does the present continent. Had it done so, more traces 

 would have been left of such extension in the South Sea Islands on 

 the one side or in South Africa on the other. 



But if the subtropical flora and fauna had in the Tertiary extended 

 unbroken across the pole from Fuegia to Tasmania, what then 

 became of the ancestors of the present subantarctic and south alpine 

 life ? Why were not these frigid forms driven from off the face of the 

 earth when the heart of the Antarctic itself enjoyed a genial climate? 



The discovery by Sir E. Shackleton of a plateau 10,000 feet high 

 near the South Pole suggests a solution of the difficulty. If such a 

 plateau existed when the climate was at its warmest, then the tropical 

 migrants could have found a congenial climate on the coast, while 

 the ancestors of the Kosciusko and Kerguelen plants and animals 

 took refuge on the plateau heights. The inference is that such a 

 plateau did then exist. 



If the land connection between the Antarctic and Tasmania had 

 broken down during the warmest period of the interglacial phase, 

 it would have isolated the flora and fauna at a time when the cold 

 elements were gathered together on the central plateau heights, 

 while the temperate and subtropical elements possessed the Antarctic 

 periphery. In that case the cold forms would have had no oppor- 



1 Ortmann (Proc. Am. Philos. Soc, xli, 1902, p. 340) considers that the fresh-water Crustacea Parastacidae 

 spread from Australia into Antarctica and thence into Chili. But the distribution of this group in Aus- 

 tralia as detailed by 0. Smith (Proc. Zool. Soc, 1912, p. 149) appears to me to be that of immigrants from 

 an east and west base, respectively. 



