president's address. 599 



render it probable that there was land in Australia in Archaean 

 time, the twilight of geological history. No evidence has yet 

 been obtained in Australasia to prove unconformabilities in 

 the Archaean Group, as has been done in North America 

 and Canada, where the Pre-Cambrian Group contained in the 

 Algonkian and Fundamental Complex is now known to comprise 

 no less than four unconformable systems. In the succeeding 

 Lower Cambrian formations, typically developed at Yorke's 

 Peninsula, a hiiijhly inteiesting contemporaneous marine fauna is 

 developed, with the character of which the labours of Professor 

 Tate and Mr. R. Etheridge, junr., have now made us well 

 acquainted. No less than four or five of the seven subkingdoms 

 of the animal kingdom are represented in that life zone, which in 

 Australia, as well as in Europe and North America, is charac- 

 terised by the trilobite Olenellus, and the pteropod Salterella. 



In the Macdonnell Kanges Mr. H. Y. L. Biown's evidence 

 shows that the Cambrian sediments were folded partially at all 

 events before the deposition of the succeeding Lower Silurian 

 sediments. The axes of folding of the Cambrian strata in 

 Australia and Tasmania appear to have followed approximately 

 the direction of the Tasmanian and Adelaide Axes. 



The frequency of conglomerate beds in the Cambrian rocks of 

 South Australia implies probable proximity of land. In New 

 Zealand the Pre-Silurian schists and other crystalline rocks of 

 the North- West end of the South Island and in Otago were 

 folded along the N.E. and S. W. axes chiefly, swinging round to 

 S. and S.S.E. at the S.E. end of the South Island, as shown by 

 Captain Hutton. The close of the Cambrian Period, therefore, 

 in Australia witnessed the second folding to which the earth's 

 crust in Australia was subjected. This second folding probably 

 increased the land area, as the next system of rocks, the Silurian, 

 covers an extensive superficial area and attains in places an enor- 

 mous thickness, which implies an extensive land surface, from the 

 denudation of which its materials were derived. The superficial 

 area covered by Cambrian rocks in Australia and Tasmania, as 

 far as at present known, is perhaps not more than about 10,000 

 41 



