261 
To study these beds in their vast extent and most inter- 
esting features it is necessary to see them as developed in the 
Flinders Ranges. On the western side of Mount Remark- 
able they comprise the Black Range, where they have a dip 
to the west. Further north, near Wilmington, they form the 
eastern flanks of the vast anticlinal fold of Horrocks Pass; 
and then, in the neighbourhood of Quorn and northwards, 
they spread out and form the ranges of the Northern Flin- 
ders, and in low exposures can be traced in the eroded hol- 
lows separating the cretaceous outliers along the southern and 
western shores of Lake Eyre. Fine examples of their rugged 
peaks and steep declivities flank the railway from Mern 
Merna to Parachilna, and include, at no great distance, the 
great synclinal fold of the Wilpena Pound. The Farachilna 
Pass to Blinman is one of the most impressive pieces of rock 
Scenery that exists in the State. The bare hills, of great 
height and deep chocolate colour, exhibit scoured sides and 
rugged outerops that can be followed by the eye for miles, 
with all the distinetness of a blackboard demonstration. In 
places faults of great magnitude are seen to cleave the hills 
in broken and contorted lines. In this latitude the purple 
slates series is continuous, from the railway eastwards to 
Frome Hill, a distance across the strike of fifty miles. The 
Blinman Mine is in this series, and owes its existence to a 
fault in the rocks in close association with an igneous dyke. 
One of the most striking features of this division is the 
prevalence of limestones of varying thickness, up to about a 
hundred feet. Some of these limestones are composed almost 
exclusively of the remains of Archeocyathince, which must 
have formed thick reefs in the Cambrian sea. Several paral- 
lel outcrops of thick limestones carrying these remains were 
Observed in a recent visit, and in some instances traced for 
many miles along the strike. In the neighbourhood of Wir- 
rialpa Station a number of thinner beds of limestone occur, 
exhibiting remarkable colitic and other forms cf structure; 
and in some of these limestones brachiopod remains were 
found in considerable numbers, running in fossiliferous 
bands. I can but briefly refer to these features at present, 
leaving for a future occasion a more detailed description of 
this interesting district. | 
The age of the purple slates division is determined as 
Lower Cambrian, * from its Archeocyathine, Salterella, 
Microdiseus, and associated forms. It was mv good for- 
