254 Transactions. — Zoology. 



of the Mammals southwards. Now a few Marsupials are known in the 

 triassic period, but it is quite possible either that they spread very slowly, 

 or that barriers existed that prevented any southward migration. In the 

 eocene period, however, some placental Mammals were in existence, although 

 Marsupials, not of Australian types however, still formed in Europe the 

 principal mammalian life; and if the supposed barriers to a southward migra- 

 tion were still in existence, we know, from what hapjDened in the Northern 

 Hemisphere, that the whole, or nearly the whole, of the Marsupials would have 

 been exterminated. The Marsupials, therefore, must have migrated south not 

 later than the eocene period, and as we know that our connection with Aus- 

 tralia and South America must have been before that migration, it follows that 

 the first, or lower cretaceous period of upheaval, must have been the time of 

 the antarctic continent. This is rendered still more probable by the fact that 

 our Jurassic fossils show a connection with Australia only, while our upper 

 secondary fossils show for the first time a relation to South America. The fact, 

 too, of the cretaceo-oolitic rocks of Tierra del Fuego having been largely dis- 

 turbed, metamorphosed, and broken through by dykes of green-stone, shows 

 that extensive elevatory movements have taken place there, also, since they 

 were deposited. It is therefore to the lower cretaceous period that we must 

 probably look for the time of the dispersion of the Struthious birds. With 

 regard to the date of the second, or Polynesian continental period, the only 

 zoological evidence we have is that it probably preceded the wide dispersion of 

 the Hemiptera, and the butterfly section of the Lepidoptera. This, therefore, 

 could not have been later than the eocene, for a fossil butterfly {Vanessa pluto) 

 has been found in the lower miocene deposits of Radaboj in Croatia, and fossil 

 Heteroptera in the miocene beds of CEningen in Switzerland. The elevation 

 during the lower eocene period was therefore probably the one which formed 

 the continent that I have described as including New Caledonia and some of 

 the Pacific Islands. At this period probably Northern Australia was sub- 

 merged, and the southern portions of Australia and Tasmania formed one 

 large island, while New Guinea, including the Solomon Islands and New 

 Hebrides on the south, and the Molucca Islands on the north, formed another 

 large island, divided from the New Zealand island, or continent, by the 

 straits between New Caledonia and the New Hebrides. 



This was the time of the migration from China southwards, and it is 

 worthy of notice tliat at the same time a large ocean existed from southern 

 Europe to China, in which the nummulitic limestone was being deposited; 

 Would it be too bold to speculate ' that it was along the shores of this ocean 

 that those fish, crustaceans, and shells migrated, which are now found in the 

 North Atlantic or Mediterranean on the one hand, and in China or Japan on 

 the other, but not on the southern shores of Asia ; and that the anomalous 



