IIOKN EXPEDITION — SUMMARY. 187 



The (jut'stioii with regard to tlie extiinial ivlatiuii.s of tlie picseiit fauna of the 

 AuHtraHan region so far as its alliiiity with tliat of South America and Australia is 

 concerned may perhaps lie hr'ietly summed up somewhat as follows. The principal 

 elements in the fauna, the distribution of which has to be accounted foi', can Ije 

 divided into two groups — (1) a smaller one, which is common to Polynesia, 

 Australia and South America ; (2) a larger one, common only to South America, 

 and Australia. The former includes forms sucli as Acanthodrilus, Microphyui'a 

 and Galaxias. The latter includes forms such as Gundlachia, Aphritis, Haplochiton, 

 Geotria, Cystignathous frogs, and certain closely-allied South Ameiican and 

 Australian Marsupials. 



It has been suggestetl that a land connection via Polynesia, between South 

 Australia and Patag<jnia, would sullice to explain the distribution ; but even if we 

 suppose* that " the Polynesian mannaals (if they existed) were drowned out by 

 submergence," in which case one might ask what would happen to the other 

 elements of the fauna such as fiesh-water fish, land mollusca, earthworms and 

 struthious birds, such a single connection will not suffice to explain matters. 



Any such C(jnnection via Polynesia was either with the very north-east of 

 Austi'alia or with the latter via a Papuan land ; but if we take into account the 

 distriljution in Australia of the two groups of animals concerned we find that the 

 second and moi'c important group is essentially, except in the case of Cystignathous 

 frogs, a group of south-eastern and Tasmanian forms, whilst neither Acanthodrilus 

 nor Micropliyura occur in this part, but are on the contrary essentially north antl 

 north-eastern foi'ms. 



No single land connection such as the one suggested will serve to account for 

 the facts of distribution and certainly not one via Polynesia. 



Assuming, as we are practically now obliged to do, some southern form of 

 land connection between Australia and South ximerica, the history of this may 

 have been somewhat as follows. 



Perhaps in late Cretaceous times both what is now Patagonia on the one hand 

 and a southern extension of Australia across Tasmania on the other hand were in 

 connection with the land ma.ss to which Mr. Forbes has given the name of 

 Antarctica. At an early period and certainly before any mammalian life had 

 reached this land a southern extension of the New Zealand land area was, for a 

 short time only, in connection with the same and so gained the elements in its 



* (,/., Lydekker, " Geotfraiihical History of Maiuiiialia," )>. 1-27. 



