chap, xin.] THE AUSTRALIAN REGION. 399 



know they have in the north. Perhaps a more important conr 

 sideration is, that Didclphys is a family type unknown in Aus- 

 tralia ; and this implies that the point of common origin is very 

 remote in geological time. But the most conclusive fact is that 

 in the Eocene and Miocene periods this very family, Didel- 

 phyidse, existed in Europe, while it only appeared in America 

 in the Post-pliocene or perhaps the Pliocene period ; so that it 

 is really an Old- World group, which, though long since extinct 

 in its birthplace, has survived in America, to which country it 

 is a comparatively recent emigrant. Primeval forms of marsu- 

 pials we know abounded in Europe during much of the Secondary 

 epoch, and no doubt supplied Australia with the ancestors of 

 the present fauna. It is clear, therefore, that in this case there 

 is not a particle of evidence for any former union between 

 Australia and South America ; while it is almost demonstrated 

 that both derived their marsupials from a common source in the 

 northern hemisphere. 



Birds offer us more numerous but less clearly defined cases of 

 this kind. Among Passeres, the wonderful lyre bird (Menura) 

 is believed by some ornithologists to be decidedly allied to the 

 South American Pteroptochidae, while others maintain that 

 it is altogether peculiar, and has no such affinity. The Aus- 

 tralian Pachycephalidae have also been supposed to find their 

 nearest allies in the American Vireonida?, but this is, perhaps, 

 equally problematical. That the mound-makers (Megapodiida;) 

 of the Australian region are more nearly allied to the South 

 American curassows (Cracidse) than to any other family, is per- 

 haps better established ; but if proved, it is probably due, as in 

 the case of the marsupials, to the survival of an ancient and 

 once vade-spread type, and thus lends no support to the theory 

 of a land connection between the two regions. A recent author, 

 Professor Garrod, classes Phaps and other Australian genera of 

 pigeons along with Zenaida and allied South American forms ; 

 but here again the affinity, if it -exists, is so remote that the ex- 

 planation already given will suffice to account for it. There 

 remain only the penguins of the genus Eudyjjtes ; and these 

 have almost certainly passed from one region to the other, but 



