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 happened 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 eretaceo-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 Ciningen 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 that 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 
