FAUNA AND FLORA OF NEW ZEALAND. . 7 
kinds were abundant in Europe and in America in eocene times, 
and as we know that penguins inhabited New Zealand at the 
same period, it is probable that birds then existed in Australia 
also. Consequently the South American migration must have 
taken place before the eocene, and cannot be referred to a warm 
miocene period. Evidently, therefore, the existence of the South 
American element in the Australian fauna and flora requires 
some explanation which Mr. Wallace’s hypothesis does not supply. 
It was these considerations, together with the fact that the 
earthquake wave of 1868 had proved that the average depth of 
the South Pacific Ocean was not great, which led me in 1872 to 
propose the hypothesis that in the lower cretaceous period an 
antarctic continent extended northwards into Polynesia, con- 
necting Australia with South America, and perhaps with South 
Africa. I introduced the African connection solely to account 
for the Struthious birds, but I am now satisfied that Mr. Wal- 
lace’s explanation of the spread of these birds from the north is 
more correct, and no reason, therefore, remains for supposing 
that Australia was ever connected with Africa. But the evi- 
dence of a connection with South America is stronger than ever. 
Nevertheless, I now abandon the idea of an extensive antarctic 
continent, because the soundings that have been lately taken in 
the Pacific Ocean have shown that such a supposition is highly 
improbable. At the same time, these soundings have made it 
clear how the connection really took place. 
The surveys of the “ Tuscarora,” the “Gazelle,” and the “Chal- 
lenger,” have proved that a vast submarine plateau, nowhere more 
than 2000 fathoms below the sea-level, runs from New Guinea and 
North Australia in an easterly direction through the Fiji and 
Tonga Islands to Samoa, spreading south to New Zealand, and 
north to the Ellice, Gilbert, Marshal, Caroline, and Pelew Islands. 
This plateau is split into two portions by adeep narrow channel, 
which runs between New Zealand and the Kermadec Islands, 
and between New Caledonia and the New Hebrides until it 
almost reaches Torres Straits. Another submarine plateau, 
also never more than 2000 fathoms below the sea-level, extends 
from Chili in a north-west direction to the Society Islands and 
Cook’s Islands, including Juan Fernandez, Easter Island, the 
Paumotus, and the Marquesas Islands. Between Cook’s Islands 
and the Samoa Islands there is a deep channel, but whether 
this is continued into the deep sea north of Samoa, or whether 
the two plateaux are continuous, is uncertain. Mr Wild, of the 
Challenger expedition, says—“ It seems as if an almost uninter- 
rupted area of elevation crossed the whole basin of the Pacific 
in a north-westerly direction from Patagonia to Japan,’* pro- 
bably about 1500 fathoms from the surface. North of this 
plateau the ocean averages 3000 fathoms in depth. To the 
south it ranges from 2900 to 2600 fathoms, getting gradually 
shallower towards the south-east. The shallowest part of the 
* Thalassa, p. 22. 
