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Geology and Physical Geography ; 
CHAPTER IV. 
Lower Palceozoic and Metamorphic {Azoic) Rocks . Silurian 
Rocks — geographical extent . Metamorphic Rocks — ar^as 
respectively occupied by Loioerand Upper Silurian Rocks ; 
leading characteristics; general theory as to origin and 
metamorphism . The Metamorphic Rocks — “ regional ” 
aw/ “ contact Unaltered Lower Silurian Rocks— fossils. 
Upper Silurian Rocks — fossils. Physical Character of 
Silurian Country. 
Tho Lower Palceozoic rocks of Victoria have been referred, 
upon clear paleontological evidence, to the Lower (Cambro) 
Silurian and Upper Silurian groups. 
With the exception of the Lower Cambrian and Laurentian 
rocks, not yet recognised, and probably not occurring in Victoria, 
the Silurian strata arc the oldest in the world that contain 
vestiges of organic life. As surface or underlying rocks, they 
occupy the greater part of Victoria, from the sea-coast to eleva- 
tions exceeding 6,000 feet ; from the Glenelg to Cape IIowc, and 
from Cape Liptrap to the Murray, constituting the prevailing 
rock-formation of the Main Divide mountain system, and the bed- 
rock of the entire colony, except in places where the subjacent 
granites and trappean rocks have been laid bare. Taking a 
broad view of the Silurian system generally, it may bo described 
as extending across the colony in a series of sharp alternate anti- 
clinal and synclinal undulations, which form the minor folds of a 
great, more or less broken, synclinal trough, whose edges appear 
at either side of the country. 
Mr. A. R. C. Selwyn estimated the total thickness of the series, 
making allowance for the recurrence of tho same bands, at not 
less than 35,000 feet. 
The metamorphic rocks of the series, among which may pos- 
sibly be representatives of the Lower Cambrian and Laurentian 
groups, a ppear between the Wannon and Glenelg Rivers westward 
of the Grampians — where they constitute the rock-formation of 
the western terminal spurs of the Main Divide — and in the north- 
eastern or Orneo district, where they prevail over a considerable 
length of the Main Divide and the country extending north and 
south from it. 
In both the districts mentioned, the rocks of this group are 
metamorphic as regards lithological character, and are so indicated 
upon the Geological Sketch-map ; but, in geological ago, they 
appear to be Silurian as regards the period of their deposition. 
