1 20 Miscellaneous. 



Theoretical Explanations of the Distribution of Southern Faunas. 

 By Captain F. W. Hutton, F.R.S. 



After reviewing the various theories which have been offered to 

 explain the difficult and intricate problem of the distribution of 

 southern faunas, the author points out that the supposition that the 

 ancestors of certain groups migrated from the northern into the 

 southern hemisphere by the present continents, and have since then 

 become extinct in the north, explains a good deal, but fails to give a 

 full and satisfactory explanation of the whole of the facts. More- 

 over, the members of the fauna unaccounted for are old forms, and 

 consequently the means of communication which served them must 

 long ago have been destroyed. To the author a fatal objection to 

 the theory of migration by way of an Antarctic continent is ottered 

 by the following consideration. Aplacental Mammals — both Multi- 

 tuberculata and Polyprotodontia — existed in Europe and North 

 America in the Triassic and Jurassic periods, and these Polyproto- 

 dontia were, no doubt, the ancestors of the living Polyprotodontia of 

 Australia. In the Eocene strata of Patagonia remains of a large 

 number of Polyprotodontia have been found which are far more 

 closely related to the Polyprotodontia of Australia than to the Meso- 

 zoic forms of Europe and North America ; consequently a direct 

 land communication must have existed between these two southern 

 countries. Now there is strong geological and pala3ontological 

 evidence that no land-ridge existed between North and South 

 America during the Mesozoic and early Cainozoic eras ; consequently 

 we must assume that the southern forms migrated through the 

 Malay Archipelago, and, if they went to Patagonia by means of an 

 Antarctic continent, they must have passed through Australia. But 

 mingled with the Eocene marsupials of Patagonia there are a 

 number of Eutheria of typicallj' South-American character — Eden- 

 tata, Toxodontia, Typotheria, Perissodactyla, Rodentia, and even 

 Platyrrhine monkeys — Avithout any northern forms of Artiodactyla, 

 Carnivora, or Insectivora ; and it is hardly possible that these should 

 have passed through Australia without leaving any record behind. 

 The theory of the former existence of a South Pacific Mesozoic 

 continent, first suggested by Huxley, seems to be the only theory 

 left. It not only explains the origin of the Australian and South- 

 American marsupials, but also the almost simultaneous appearance 

 of different Eutherian mammals in North and South America. We 

 must suppose that this continent threw off first New Zealand, then 

 Australia, then Chili, and finally disappeared under the waves. At 

 a later date New Zealand must have formed part of a large island 

 joined to New Caledonia, but not to Australia. The objections to 

 this theory are geological rather than biological, involving the 

 doctrine of the pei-sistence of continental and oceanic areas upon 

 which geologists are not agreed ; and such objections are equally 

 applicable to the theory of an Antarctic continent. — Linn. Soc. New 

 South Wales, Abstract of Proceedings, April 29, 1896, pp. ii, iii. 



