xlv. 



press any opinion, either as to the probable age or even super- 

 position of the various rock masses forming the central moun- 

 tain chain of South Australia ; but, nevertheless, has stated 

 that " the only locality in which the rocks of that chain bear 

 any decided resemblance in mineral and physical structure to 

 the auriferous Silurian rocks of Victoria is in the valley of the 

 Onkaparinga ; and, consequently, I was at first inclined to 

 suppose that all those rocks that are doubtless higher in the 

 series — including the crystalline limestones of Einniss Tale, 

 Macclesfield, Mount Torrens, Keyne's Hill, Angaston, and the 

 Rurra — were altogether newer than Silurian. jNow, however, 

 I am inclined to think that this view is probably erroneous, 

 and that they are all true Silurian rocks. At all events the 

 difference in mineral character is no greater than exists between 

 the slaty lower Silurian rocks of "Wales and the siliceous lime- 

 stone, gneiss, and quartz rocks of the same formation in the 

 Northern Highlands of Scotland. ... I was much struck 

 Avith the remarkable accordance in lithological character and 

 general sequence of the siliceous limestones, quartz rocks, and 

 micaceous flagstones of the Durness and Assynt Silurians, with 

 that of the siliceous limestones, quartzose sandstones, and 

 micaceous slates and flags of the northern part of the South 

 Australian chain ; and I have little doubt, though rare and not 

 easily detected, that fossils will eventually be found in some 

 portion of the latter, as they have been in the Durness and 

 Assynt limestones, that will enable them to be at once assigned 

 their true position in the geological scale." 



According to the Rev. J. E. Tenison Woods (G-eol. Obser. in 

 S. A., pp. 20, 21) fossils have been found at two portions of the 

 Adelaide chain — at Willunga thirty miles south, and at Xuriootpa, 

 forty-seven miles north from Adelaide. At the former locality 

 it was reported to him that Pentamerus oblongus had been 

 found ; but from the latter, a fossil which had been collected 

 by his brother has been recognised by the Rev. J. E. T. "Woods 

 as Cruziana cucurlita — a species of algae described from the 

 Silurian rocks of Bolivia. Until the observation of the 

 occurrence and identification of Pentamerus oblongus be A'erified 

 it would be well to expunge it from our list of local fossils ; 

 indeed the Rev. Mr. Woods inclines to its rejection. And as 

 the very nature of the fossil, Cruzlrma cucurbita, precludes it 

 from being used as a test of geological age, I conclude that the 

 Lower Silurian age of the rocks of the Adelaide chain is not 

 proven. Indeed, recent discoveries, which have been com- 

 municated to this Society by Mr. Tepper, necessitate their 

 relegation to a much more ancient ejDoeh. The chief facts are — 

 that in the neighbourhood of Ardrossan, a lower series of 

 metamorphic slates and limestones is covered unconformably 



