xlviii. 



Orthis calligrcmima, a characteristic Lower Silurian fossil. The 

 matrix is a calciferous sandstone of a grey colour. 



Though Mr. Selwyn has not assigned the upper unconform- 

 able series to any geological epoch, yet he leads us to infer the 

 probability of its belonging to the Devonian period. Another 

 geologist, Mr. Ulrich, who has had opportunities for forming 

 an opinion upon the successional order in the rocks to the 

 north from Port Augusta, does not fully confirm the observa- 

 tions of Mr. Selwyn. He says, " I agree with him, for the 

 same reasons he advanced, in unhesitatingly assigning thein to 

 one of the older epochs of the Palaeozoic period — -the Lower 

 Silurian being perhaps the most likely one. Owing, probably, to 

 my rapid mode of travelling, I was not able, however, to 

 recognise the features upon which Mr. Selwyn based their 

 subdivision into older and newer ; for, throughout the country 

 traversed, from the Burra northward, I saw no evidence of any 

 unconformity in the strata ; they seemed to me to represent one 

 and the same grand series, only in places more or less meta- 

 morphosed by contact with intrusive rocks." (Mineral Ke- 

 sources north of Port Augusta, Pari. Pep., p. 18). 



The discoveries made by Mr. Tepper, and referred to on p. xlv. 

 confirm Mr. Selwyn's opinion that our Palaeozoic rocks belong 

 to widely separate periods ; but they, at the same time, 

 necessitate an alteration in the terms by which they have been 

 designated. The fossils, which have been obtained from the 

 thick " Parara" limestone, overlying mica slate, marbles, &c. (see 

 Tepper's paper, Phil. Soc, Adelaide, p. 71), consist chiefly of 

 heads and other fragments of a species of blind trilobite, pro- 

 bably an Olenus; but other foi*ms observed are several examples* 

 of a small species of JEcculiomphcdus, a Oapulus, slender conical 

 casts of an Ortlioceras or Creseis, and fragments of corals (some 

 of which showing a cystiphylloid structure). That we have 

 herein a Silurian facies is not likely to be questioned ; but to 

 what group of the Lower Paloeozoic rocks should the lime- 

 stones yielding the fossils be referred, is a question that had 

 better be reserved till more tangible evidence is forthcoming. 

 That we are on the eve of a great discovery, so far as concerns 

 the classification of South Australian Primary rocks, must be 

 conceded. 



MESOZOIC. 



Jl'eassic. — The Eev. W. B. Clarke, in his " Sedimentary 

 Pormations of New South "Wales," p. 84, does not credit South 

 Australia with the possession of Mesozoic rocks, fossiliferous 

 evidence of which had been publicly made known previous to 

 the publication of that work. He had evidently overlooked 

 the very brief announcement made by me, Quart. Jo urn. 

 Geol. Soc, p. 258, 1877, that Belemnites allied to B. australis, 



