﻿Vol. 64.] CAMBEIAIs^ AGE IIT SOUTH AUSTEALTA. 237 



The order of succession in the beds is perfectly clear (see fig. 1, 

 p. 236). In the Sturt Eiver, near Adelaide, the glacial beds are 

 seen to underlie the Tapley's-Hill Slates. The latter pass up into 

 calcareous slates, which, near Brighton, become a very pure lime- 

 stone, oolitic in structure, bluish in its lower portions and reddish 

 in the upper. A buff-coloured, dolomitic limestone rests upon the 

 latter, and is overlain by purple slates, thin quartzites, and lime- 

 stones of the same colour, which form a coastal belt of rocks, half 

 a mile wide. Passiug under the sea, they reappear under similar 

 lithological features (including Archceoci/atMna-Ijimestones), on the 

 opposite side of Gulf St. Yin cent. 



The importance of the purple-slate division is not apparent 

 from the section visible near Adelaide, as for the most part it is 

 covered by the waters of the Gulf over a width of nearly 40 miles. 

 In the Flinders Eanges these chocolate-coloured rocks have a great 

 development, and comprise the whole of the mountain-ranges in a 

 50-mile section, occurring between Parachilna (on the Northern 

 Eailway-line) and the western side of Lake Frome. Between 

 Parachilna Gorge and Wirrialpa (40 miles), the beds form a vast 

 dome, Blinman occupying the centre of the curve, and the Archceo- 

 c?/a^7ima-Limestones crop out at both extremities, exhibiting 

 reversed dips. 



While no distinct unconformity can be recognized in this series, 

 a convenient division is established by regarding the Brighton 

 Limestones as a dividing-line between the lower and the upper beds. 

 Such a division is supported by geographical as well as by litho- 

 logical considerations : the Mount-Lofty Eanges being typical of the 

 former, and the Flinders Eanges of the latter ; while a purple or 

 chocolate coloration is characteristic of the beds above this line of 

 division, but is not present in the beds below that line. 



Although this very thick series includes numerous limestones, 

 of greater or less development, it is only at two horizons that fossils 

 have been definitely determined. The more important of the 

 two is distinguished by Archceocyatliina-mOiihle^, which must have 

 formed coral-reefs in the Cambrian seas fully 200 feet thick. The 

 corals are thickly crowded together and beautifully preserved. In 

 some localities they occur as chalcedonic pseudomorphs, which 

 weather into relief. Mr. T. G. Taylor, B.Sc, of Sydney, is engaged 

 on the elucidation of these forms for description. 



The fauna of the ArcluEOcyathina-VD.dM.es, (as hitherto described ^) 

 comprises the following forms : — 



ArcheeocyathincB (m great variety) of Hyolitkes communis, Billings, 

 which the rock is mostly composed. Hyolithcs couularioides, Tate. 

 Steiiothcca riigosa. Hall. BolicJiometopus Tatei, H. Woodward. 



Ophileta suhangulata, Tate, ! Ptychoparia australis, H. Woodward. 



PLaiyceras Eiheridgei, Tate. 

 Amhonyckia macropiera, Tate. 

 Orthisina compta, Tate. 

 Orlhis (?) peculiaris, Tate. 

 Salter ella planoconvexa, Tate. 



Ftychoparia Hoiuchini, Eth. fil. 

 Olenellus (?) Pritchardi, Tate. 

 Microdisciis suhsagittatus, Tate. 

 Lcperditia sp. 

 Hyalostelia. 



1 Op. jam cit. & ' A Further Cambrian Trilobite from Yorke Peninsula ' 

 R. Etberidge, Jun., Trans. Roy. Soc. S. Austral, vol. xxii (1897-1)8) p. 1. 



