38 A. W. HOWITT ON THE PHYSICAL GEOGRAPHY AND 
We find that the Upper Silurian Limestones of the Gibbo River, 
and also those of the Limestone River, which I regard as probably of 
the same age, are part of the great general group of Lower Paleozoic 
formations which I have described by the term ‘“‘ the Lower Paleeozoic 
foundation” of North Gippsland. We may therefore not unreasonably 
infer that those great changes in the earth’s crust continued to the 
close of the Silurian period. The surface of all these Silurian strata 
‘shows the long ages of denudation which must have elapsed before 
the succeeding Devonian groups, as we see them, were laid down. 
This long period seems to have been one of volcanic activity. The 
“‘Snowy-River porphyries” show the extension, and the Wombargo 
Mountain reveals to us the structure, of these ancient volcanos. 
Isolated hills of quartz-porphyries and allied rocks which have pene- 
trated the Silurian and the granite suggest strongly the idea of cases 
of similar voleanos from which the ejected materials have been de- 
nuded, but which are still to be recognized in the large percentage 
of felstone and porphyry pebbles in the accumulations of Tertiary 
marine gravels surrounding them. 
That these Paleozoic voleanos were subaerial, and probably ter- 
restrial, may be inferred from the fact that the great piles of felstones, 
ash, and agglomerates now remaining contain no beds which I can 
recognize as aqueous; and this inference would accord with the fact 
that, so far as our present paleontological evidence extends, no 
Lower Devonian marine strata exist; for the Buchan and Bindi 
Middle Devonian limestones rest on the Snowy-River porphyries, 
and these latter upon the Lower Paleozoic rock masses. 
But if the Lower Devonian period was thus one of terrestrial 
conditions, it follows that the succeeding period was one of sub- 
sidence of the land. Denudation must have been very great over 
the Snowy-River porphyries, over the Silurian and the metamorphic 
schists, the granites and quartz-porphyries, before the marine lime- 
stones of Buchan, Bindi, Gelantipy, and elsewhere were deposited. 
To the westward, somewhat similar marine conditions accom- 
panied the formation of the 'Tabberabbera shales and limestones. 
During this Middle Devonian period I am unable as yet to 
recognize any traces of volcanic action. 
Succeeding this period, we have equally clear evidence of great 
and long-continued movements of the earth’s crust. The Bindi 
limestones were denuded; the Tabberabbera shales and sandstones 
were tilted at a high angle, folded, and apparently denuded even 
more than the Bindi limestones. We no longer have strata con- 
taining a well-marked marine fauna; but the beds of Iguana Creek 
and of Mount Tambo only yield us somewhat scanty traces of a terres- 
trial flora; while the shales and limestones of Cowombat and the 
Native-Dog Creek appear to me to indicate a shallower sea or a 
nearer proximity to land than the Buchan and Bindi beds. 
The Upper Devonian conglomerates, sandstones, and shales suggest 
the proximity of land; and volcanic activity is again apparent in the 
felstones and felstone ash, somewhat resembling the older accu- 
mulations at Wombayo and the Snowy River. But these volcanic 
