20 



cal geology. The distinct and comparatively quiet area of 

 Australia was hence tenanted by the same species, whilst vast 

 biological and geological changes took place in the European 

 area, formerly considered the type by whicli all others would 

 be compared. He adds that the extinction of Australian vol- 

 canoes, and the change in its coral flora, were grand phe- 

 nomena, which he also regards as contemporaneous with the 

 upheaval of the Alps, Himalayas, New Zealand, and the 

 closure of the Isthmus of Panama. He points out the enor- 

 mous denudation of the Australian area from the thickness 

 and extent of unfossiliferous deposits which cover the marine. 

 During the glacial period of Europe, he suj^poses that sub- 

 aerial denudation went on. The gold drifts, sandy ferruginous 

 clays, coarse j^ebble grits, and hard ironstone, cements and 

 conglomerates with the lava plains north of Cape Otway, are 

 of this age, and younger than the polyzoic limestones. 



To all these conclusions I would readily subscribe, except to 

 that portion which supposes Northern Australia completely 

 submerged, and no land to have been north of the tertiary sea. 

 The following are facts on the subject: — 1. The tertiaiy 

 marine fossiliterous beds thin out rapidly as they are followed 

 north. In the south-east portion of the continent this occurs 

 in a few miles, and in any case they are not known further 

 than 30deg. S. lat. 2. The enormous development of upper 

 secondary beds in the north of the continent, and their com- 

 plete absence from the south. This seems to show that North 

 Australia has escaped the general tertiary denudation, which 

 would not have been so had these bedsbeensubmerged. Besides, 

 they are very soft in character, and so horizontal, that 

 they do not appear to have suffered any disturbance 

 in tertiary periods. Thirdly, the only tertiary rocks 

 which are found in North Australia appear to be either 

 subaerial or lacustrine. Last of all, the physical geology of 

 the tertiary deposits serve to show that the sea encroached 

 upon the present area of Australia in a great horse shoe form, 

 and that the contour of the continent gives a good general 

 idea of the shape of the great tertiary sea basin. Add 

 to this that the flora and fauna of the land seem to be a 

 connecting link with the secondary fauna and flora of Europe, 

 which is very easily understood, if we suppose a part of the 

 Australian continent to have been undisturbed. South 

 Western Australia possesses these features in the most marked 

 way, and this is the portion of the land, too, where the 

 physical geology is against the supposition of any submersion.* 



* Dr. Hooker says the Australian orders (abundant there and rare else- 

 where) are very unequally distributed in Australia. There is a greater 

 specific difference between S.E. and S.AV. Australia than between Australia 



