ANTARCTIC ZOOGEOGRAPHY 357 



emphasizing the transitions, sometimes gradual and again sharp, 

 which the marine flora and fauna reveal. 



Former Land Connections 



Some aspects of distribution have been interpreted as supporting 

 theories of early land bridges, which would connect the old Antarctic 

 Continent with South America, Australia, and perhaps with Africa. 

 In fact, the reconstructions which cause certain maps of distribution 

 to resemble seventeenth-century charts of the Terra Australis are 

 based more often upon the inferred migration routes of plants and 

 animals than upon any accepted geological evidence. As recent 

 an investigator as Benham,^ however, believes that he has exhausted 

 all the possibilities under existing geographic conditions without 

 accounting for the distribution and relationships of oligochaets, in- 

 sects, spiders, and terrestrial crustaceans at the sub-Antarctic islands. 

 He maintains that the facts demand either land bridges during early 

 Cenozoic time or such a juxtaposition of Antarctica with Austraha 

 and South America as is postulated by the Taylor- Wegener hypothesis. 



In favor of certain less extensive land connections there is, indeed, 

 evidence from many sources. It is more than probable, for example, 

 that during the early Tertiary Antarctica may have been linked up 

 with Fuegia by closely spaced islands over the route which passes 

 through South Georgia, the South Sandwich group, and the South 

 Orkneys. But as regards major continental offshoots across the 

 present deep-water areas by way of "Gondwana Land" or otherwise, 

 the zoological evidence seems to be inconclusive when not actually 

 unfavorable. 



Regan^ denies that the southern fishes show any indication of 

 land bridges and concludes that the Antarctic Continent has been 

 washed for a long time, perhaps throughout the greater part of the 

 Tertiary, by an ocean of extremely low temperature. Much has been 

 made, this author notes, of the distribution of the eel gudgeons 

 (Galaxiidae) , the supposed fresh-water fishes of South Australia, 

 Tasmania, New Zealand, and the southern parts of South America. 

 Galaxias attenuatus, for example, is a species common to all these 

 regions; but it has now been demonstrated that the fishes of this 

 family breed in the sea and that they are salmonoids of marine origin. 

 The evidence from the distribution of mammals has also been re- 

 viewed by Regan, who agrees with many earlier workers regarding the 

 lack of true relationship between theTasmanian "wolf" (Thylacinus) 

 and the Patagonian Miocene marsupials known as Borhyaenidae. 



1 W. B. Benham: OHgochaeta of Macquarie Island (Australasian Antarctic Expedition 191 1- 

 1914, Scientific Repts., Ser. C: Zoology and Botany, Vol. 6, Part IV, pp. 1-38), Sydney, 1922. 



-C. T. Regan: Fishes (British Antarctic ("Terra Nova") Expedition 1910, Nat. Hist. Repts.: 

 Zoology, Vol. I, pp. 1-54), London, 1914. 



