41 



of depression followed, during wliich the table-land formation of 

 clays were deposited on all points except the actual crests of the 

 range. 



6. Another uprising ensued, since which the table-land deposits 

 have been continually undergoing removal, and now only portions 

 remain flanking the range. Of this the eastern side, being on 

 the side of quickest drainage, has almost disappeared, while the 

 western side is still sufliciently continuous to form a great pro- 

 portion of the range. 



The Great Austral Plain. 



We have already some knowledge of portions of the great plain 

 through the geological observations made by the geologists of the 

 the adjoining colonies near our boundary line, and public works 

 undertaken by our own Government along the shores of Lake 

 Eyre. 



Long previous to the official statements recognising the Meso- 

 zoic age of the Lake borders. Professor Tate, then President of 

 this Society, had critically examined all available data connected 

 with the region, and declared positively in his anniversary address 

 that a large Mesozoic formation, probably of Jurassic age, occupied 

 a large part, if not the whole, of the Lake Eyre basin. Since then 

 the deep bores of the Water Conservation Department and the 

 continued collection of fossil evidence from various localities have 

 changed the presumptive into positive, and we now know that the 

 Tertiary and Cretaceous formations which extend west of the 

 East Coast Range not only cross our boundary from the eastern 

 colonies, but there is good reason to believe that in the latitude 

 of Lake Eyre, at least, they extend right across our whole pro- 

 vince. The furthest westward from which fossils have been ob- 

 tained from this formation is on the Arkaringa Creek, about 70 

 miles west of the Peake, from which place a splendidly preserved 

 portion of a cast of the Crioceros aust'rale was procured by my 

 brother (Mr. W. H. East), and through me presented to the 

 museum of the Adelaide University, where it now^ is. Curiously 

 enough, the only other specimen yet discovered is from the Flin- 

 ders River, in Queensland, on the counter slope of the great 

 plain, where its drainage turns towards the Gulf of Carpentaria. 

 Eossils identical with those occurring at Mount Margaret were 

 obtained by me from Dalhousie Springs ; and at Mount Daniel, 

 about LS miles north of Charlotte Waters, I obtained Lingula 

 suhoraJis and a piece of silicilied coniferous timber which had been 

 drilled by Xylophagas. A most remarkable feature thi-oughout 

 the whole region is the remarkable uniformity of tlie beds both in 

 sequence and composition, This is well illustrated in the sections 



