24 Transactions. 
further conglomerates, grits, sandstones, and shales with a very late Silurian 
fauna, if not actually transitional into the Devonian. Chapman (1913) 
compares the fauna of the last two formations with that of the Helderberg 
series in North America. 
Silurian rocks form the most widespread of the Palaeozoic formations 
of New South Wales, and include representatives of both the lower and 
upper divisions, as was pointed out by De Koninck in 1877, and these 
correspond to Melbournian and Yeringian series respectively of Victoria. 
The palaeogeographic conditions, however, seem to have been somewhat 
complex, and we will not here attempt a detailed analysis of them. The 
eastern margin of the continental nucleus extended through the region of 
the Western Plains, and littoral conglomerates lying unconformably on the 
` Ordovician (?) rocks are widespread near Cobar (Andrews, 1913). They 
also occurred farther to the south-east in the Forbes-Parkes district (Andrews, 
19104), and the Yass district (Shearsby, 1911), but are absent elsewhere, 
“while the general occurrence of alternating sandstones, claystones, an 
limestones indicates tranquil deposition in a comparatively narrow sea" 
(Süssmileh, 1914). The most extensive sequence of fossiliferous beds is in 
the Yass district. In the shales, sandstone, and limestone of the lower 
portion, Tryplasma, Pachypora, Cyathophyllum, and Halysites occur, with 
some brachiopods; while in the upper portion there is a very extensive 
Wenlock fauna, enumerated by Shearsby, containing many genera of corals, 
brachiopoda, mollusca, and trilobites, of which the following are present : 
stromatoporoids, Favosites, Heliolites, Halysites, Pleurodictyum, Zaphrentis, 
Tryplasma, Cyathophyllum, &c., sometimes with Orthoceras and Astylospongia. 
Some forms had a wide range, whilst others were confined to limited areas ; 
but the meaning of this distribution has not yet been fully investigated 
). 
hone : ро 
ы трак eee Pentamerus. Ball (1918) thinks the slates and limestones 
= e Cloncurry district of north-western Queensland may also be of this 
| T noceras and Ort. 'atit to- 
pora (Etherid ‚1911; bet vee, hoceras, Orthoceratites and Stromato 
"urian rocks are known in New Zealand al At Reef in the 
north-west of the South Isl Се шиш Au 
(Henderson, 1917) сау AF 
are found th - : 
h ad ges. water sedim ents, calcareous argillites. Thomson (1913) 
s regions, but so far as is indicat е faunal facies in the 
oder E by the provisional ublished) 
terminations of Dun and Chapman both are be with the Upper 
