Harrison—On the Geology of Hobart Town. 495 
upon the subject, stated his belief that the bone in question was found 
in beds situated above the coal. It is with extreme diffidence that 
I venture on a conclusion contrary to that of a gentleman whom I 
believe to be both an enthusiastic and a careful observer; but, from 
a rather rapid examination of the beds in question, I had certainly 
thought differently. The section (fig. 2, p. 493) will show both the 
position of the fossil, and also the nature of the rocks adjacent. 
It will be seen that, from the western boundary of the stripe of 
basalt occupying the ‘Domain,’ to the sandstone of ‘Knocklofty 
Terrace,’ the strata present a gradually ascending series of outcrops ; 
although it is more than probable that, in consequence of faults, the 
sum of the outcrops is not exactly an expression. of the real thickness 
of the series exposed. 
At the point B (Trinity Church) beds very low in the succession 
appear on the surface, the upper ones having evidently been de- 
nuded. As the coal-seams appear to lie near the top of the series, 
it is plain that a comparatively small amount of denudation would 
remove both such seams, and also a portion of the immediately 
underlying sandstone. ‘The position of the beds wherein the fossil 
was discovered, close to the Government House, near the centre of 
the valley of the Derwent, would seem to give no promise of being 
spared the influence of denuding agencies; so that although through 
faults, the points B (Trinity Church) and C (Knocklofty Terrace) 
are evidently more upheaved and denuded than the ground near 
Government House, it is hardly probable but that some strata were 
cut off from the latter locality also; and as I believe no coal-beds 
have been discovered thereabouts, it seems but reasonable to suppose 
that the carbonaceous strata have been swept away, and that the 
beds now remaining, although of newer age than the claystone of 
Trinity Church, are decidedly of older age than the coal.* This 
would make the fossil referred to of great use in determining the 
geological position of the Tasmanian beds, and show that they were 
deposited, at the very least, during the existence of the Batrachian 
forms of the Secondary period. 
It may be asked, as the limestone is of Paleozoic, and the coal of 
Mesozoic age, whether the surface was. unsubmerged during the 
intervening time, or whether there has been a subsequent removal 
of rocks once deposited ? 
Perhaps it will appear that neither of these alternatives is abso- 
lutely required. The Permian group may, after all, be represented 
by a portion of the strata intervening between the two formations, 
although, through the absence of fossils, evidence of such fact is 
nowhere discernible. ‘The Magnesian Limestone may have been so 
far local as to be excluded altogether from Tasmanian waters. Pro- 
bably the beds, during the course of their deposition, resembled not 
a little the accumulations of sand now gathering upon the coasts 
both of Tasmania and Australia ; deposits which, it is likely, will 
be entirely barren of fossils. Such beds would necessarily present 
* T have dwelt particularly upon the above facts, since they appear to bear so 
especially upon the question of the age of the Australian coal-deposits. 
