III.] NORTHERN ORIGIN OF SOUTHERN FORMS. 1 29 



animals assumed to be essentially southern, really had a northern 

 origin. It may be premised that, according to the view of 

 Dr Forbes, " Antarctica " followed nearly the 2000 fathom line, 

 extending northwards from a circumpolar area by broad expan- 

 sions, one to join an old New Zealand continental island (includ- 

 ing the Antipodes, Macquarries, New Zealand, and Chatham, Lord 

 Howe, Norfolk, and the Kermadec and Fiji Islands); a second to 

 East Australia and Tasmania ; a third to the Mascarene and 

 adjacent islands ; perhaps one to South Africa ; and finally one 

 to South America. 



As regards the marsupials, which are among those considered 

 to be southern types, the evidence of the northern Jurassic and 

 Cretaceous kinds alluded to in the preceding chapter, coupled 

 with the presence of opossums in the Oligocene of the northern 

 hemisphere, renders it practically certain that the group did not 

 originate in the southern hemisphere. 



Among other groups cited by Dr Forbes as being mainly or 

 exclusively southern in their distribution and origin are the parrots 

 (Psitiaci) and trogons (Trogonidce). But both these are represented 

 in a fossil state in the Oligocene strata of France, and are thus 

 shown to have been originally denizens of the temperate regions 

 of the northern hemisphere. Take, again, the case of the struthious 

 birds, or Ratitse, which although cited as a southern group, are 

 represented by an ostrich (Struthio) in the Pliocene of Northern 

 India and the Crimea, while the former deposits have yielded 

 remains of a three-toed genus allied probably to the emeus and 

 cassowaries. Much the same may be said in regard to the giant 

 land-tortoises (Testudo\ which although now confined to the 

 Galapagos and Mascarene islands, were abundant in Northern 

 India, Greece, France, and the United States during the Pliocene, 

 and also occur in the French Miocene and Oligocene, as well as 

 in the Plistocene deposits of the Maltese caves. The group was 

 thus evidently a northern one originally, and as it is unknown in 

 the southern hemisphere before the Pampean epoch of Argentina 

 and the superficial deposits of Madagascar, its southern migration 

 probably did not take place till the Miocene, or even the 

 Pliocene. Indeed, the separation of North and South America 

 indicates that, if the Galapagos tortoises came from the former 

 L. 9 



