214 
Geology of Sydney. 
giant lycopod Lepidodendron flourished. The last- 
named plant is one of the oldest representatives of the 
vegetable kingdom known in 
Australia. There was dry land, 
no doubt, in Silurian times, but 
no trace has yet been discovered 
of the vegetation with which it 
was clothed. The oldest land sur- 
faces of which we have evidence 
in Australia, appeared as dry land 
in Devonian times. 
The great thickness of the 
Devonian sediments is remark- 
able. At Mount Larnbie, near 
Rydal, on the western line, Mr. 
Wilkinson measured a section 
not less than 10,000 feet in 
thickness. It is evident, there- 
fore, that the area over which 
such an accumulation of sedi- 
ments was deposited must have 
been subsiding for a very long 
Fi(i . 59. — Murchiso via 
turns, 1 de Koninck. A Our present knowledge 
lower Palaeozoic fossil . .. n , , 
shell from near Yass hardly justifies any attempt to 
(N.S.W.) picture the physical geography 
of Devonian times. As no traces of Devonian beds 
are found on the eastern slopes of the Blue Mountains, 
we may assume that the old Devonian sea stretched 
1 De Kuninck : Atlas of New South Wales Palaeozoic Fossils. Plate iv. 
