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north-east of Willunga.* This important find demonstrated 
a definite Cambrian horizon striking through the heart of 
the Mount Lofty Ranges. A suggestion from the writer, 
that this discovery had great significance in relation to the 
geological age of the Mount Lofty Ranges, and might require 
a reconsideration of the position, was met by Professor Tate, 
in the discussion which followed the reading of the paper, 
with strong opposition. The professor stated that “the beds 
in which the fossils were found probably constituted only a 
spur of the ranges, and did not affect the question in its 
bearings on the age of the Mount Lofty Ranges as a 
whole." 
The subject had reached such an interesting stage that no 
other stimulus was required to pursue it further. ^ After 
several years of field study, directed to this object, I have 
now the honour to place the results of my observations before 
the Society as a first contribution towards a systematic eluci- 
dation of the structure and succession of the older rocks of 
this State. 
The existence of a bed in the series with such distinct 
lithological characteristics as that possessed by the older 
glacial till, and its remarkable persistency, have greatly 
simplified the work attempted; for wherever this bed occurs 
it supplies a datum line from which the geological section 
can be interpreted and the associated beds placed in their 
consecutive order, even in the most remote localities. 
I have taken the country in the neighbourhood of Adelaide 
as the type district of the series, and the beds which out- 
crop between Mount Lofty and the sea may be regarded as 
the index to most, if not all, the Palæozoic rocks of the State. 
II. ORDER or SUCCESSION. 
So far as the foot hills and coastal districts near Adelaide 
are concerned, the Palæozoic beds appear to belong to a con- 
formable series, and may be subdivided into well-marked 
divisions, as shown in the following order in superposition, 
V1Z. : — 
(A) Purple slates, quartzites, and limestones—Marino, 
liallett's Cove, Lower Onkaparinga. 
(B) Siliceous, blue, pink (oolitic), and dolomitiz limestones 
— Brighton, Field River, Hackham, &c. 
(С) Banded, fine-grained clay slates and shales—Tapley’s 
Hill, &e. 
(D) Glacial till, grits, etc., with erratics—Sturt River, 
Onkaparinga River, &c. 
(E) Siliceous and felspathic quartzites and phyllites— 
Mitcham, Glen Osmond, Magill, etc. 
* “The Occurrence of Low. Cam. Fossils in the Mount Lofty 
Ranges.” Trans. and Proc. Roy. Soc. S. AS, vol. Ж, p. 74. 
