BY A. J. SHEARSBY. 281 



The close proximity of the Glenbower series of fossils, which 

 are without doubt Upper Silurian, to those of Clear Hill, which, 

 from the presence of Diphyphylium gemmiforme, Eth. fil., 

 Spirifera yassensis, De Kon., and Cho7ietes culleni, Dun, are 

 Middle Devonian, and being separated at this locality by such a 

 narrow margin of country, seem to indicate that this is the 

 probable collecting ground of the late Rev. W. B. Clarke, where 

 he obtained " the series of shells, corals, etc., from the Murrum- 

 bidgee " which he submitted to Messrs. Salter and Lonsdale; for 

 he mentions in his *' Sedimentary Formations of N.S.W." that 

 Mr. Salter's report(4) was as follows : — " These fossils are of a 

 mixed character, many being of unquestionable Silurian age, and 

 others having all the aspect of Carboniferous and Devonian 

 fossils. It will not be easy to predicate those of the Devonian 

 type, as there is much, similarity between fossils of that age and 

 those of either of the other systems. . . . But if none of the 

 fossils came from the Carboniferous beds, then there must 

 certainly be Devonian forms mixed with Upper Silurian." Had 

 Mr. Clarke made further investigations at this locality, he would 

 most likely have been able to make out the actual limits of the 

 Upper Silurian and Devonian formations, at any rate as far as 

 the Yass district was concerned. 



If the strike of the bed or belt of volcanic rocks which divides 

 the sedimentary formations of this district into two such distinct 

 series be traced three or four miles to the south-east, it brings 

 one to a range known as Nutter's Mountain, the summit of 

 which is composed of banded felsitic tuff, the intervening country 

 and that beyond consisting of jumbled masses and beds of por- 

 phyries and tuffs and tufaceous rhyolites. 



If the strike be followed in a north-westerly direction, one has 

 to travel over other high and rugged hills of porphyries, etc., till 

 at a distance of about eleven miles the Devil's Pass is reached, 

 where the Yass River has found a path through on its way to 

 join the Murrumbidgee. All along this line of country, which 

 extends for many miles beyond the Pass, are to be found outcrops 

 of galena, which in two cases have been found to be payable, and 



