THE ANTARCTIC REGIONS. 335 



been assumed, that these large and seemingly closely related birds 

 may have been independently developed in the regions which 

 they now occupy ; but in view of certain facts presented by other 

 groups of animals, especially the quadrupeds, it is probably safer 

 to assume that their origin was a common one, and that they were 

 distributed over a land surface which had union with South 

 America, Africa, and Australia, or New Zealand. Such a uniting 

 land mass was not improbably ancient Antarctica. 



Much more positive evidence bearing upon the question under 

 consideration is afforded by the composition of the South Ameri- 

 can Tertiary mammalian fauna. Up to and inclusive of the 

 Miocene period this fauna was a distinctively South American one, 

 or at least not North American. The hoofed animals represent- 

 ing various orders {Toxodontia, etc.) were of a type at that time 

 almost unknown in the north ; there were no true artiodactyls or 

 perissodactyls, and no insectivores, cheiropters, creodonts, or car- 

 nivores. The essentials of the fauna were recruited from the 

 orders of edentates, marsupials, and rodents ; the first named 

 have specifically South American types, as the sloths and arma- 

 dillos, while the last named, also specifically South American, 

 lacked the more common northern forms, such as the hares, rats, 

 squirrels, marmots, and beavers. The middle Tertiary fauna thus 

 gives evidence of the isolation of this portion of the continental 

 tract, and leans to the probability that the fauna then and there 

 existing was derived from a southern source. It is only in the later 

 or Pliocene period that we have an introduction of the northern 

 types of quadrupeds, such as the true carnivores, deer, horses, 

 mastodons, etc. Whether or not the region where this southern 

 South American fauna originated was the region of South Amer- 

 ica itself, or another land mass that was at one time united with 

 it, is not made clear by the evidence of the faunal elements that 

 have been noted ; but significant in this connection, as has been 

 pointed out by Prof. W. B. Scott, is the relationship of the 

 Miocene marsupials, which incorporate within themselves a num- 

 ber of distinctively Australian types, a condition that has been 

 properly emphasized by the investigator last mentioned as giving 

 strong evidence of a former union between the two main south- 

 ern continents. 



In explanation of the anomaly, assuming a connection between 

 South America and Australia, that none of the South American 

 mammalian types reached Australia, Prof. Scott suggests an early 

 connection between the latter region and Antarctica (and through 

 it with South America, thus permitting of a broad dispersion of 

 the marsupialian types), and then a final severance before the 

 appearance of the placental form of quadrupeds. Whether this 

 explanation will ultimately prove to be the correct one or not, 



