Upper Silurian flocks. 
39 
isolated vertical lenticular mass of limestone of the same character, 
about a couple of feet long and one foot thick, thinning out to 
nothing upwards and downwards, and entirely enclosed by the 
•slates except on the exposed face. The proof here as to the lime- 
stone being an intercalated deposit, and of the same age as the 
associated Upper Silurian slates, is beyond question. 
On palaeontological evidence the Upper Silurian rocks of Vic- 
toria have been identified as the equivalents of the Wenlock shales, 
May Hill sandstones, and Upper Ludlow rocks of England, by 
Professor McCoy, who has figured and described in his decades 
the following named fossils : — 
Petr aster Smithii (McCoy) ; Urastella Selwyni (McCoy) ; A 
Graptolite — fletiolites Australis (McCoy) ; Trilobites — Phacops 
caudatus (Brong) ; P . Jecundus (Bar.) ; Forbesia euryceps 
(McCoy); Lichas Australis (McCoy) ; and IJomalonotus Ilarrisoni 
(McCoy) ; Leptwna ( Leptagonia ) rhomboidalis (Wilck. sp.) ; Trem- 
atospira liopleara (McCoy); T. formosa (Hall); Spirifera plica - 
tella (Lin.), var. macropleura (Conrad) ; 6\ sulcata (His.) ; 
Sprig er ina reticularis (Lin. sp.) ; flhy n chonel la ( hemithijri s ) tic - 
ce mp l i cata (Sow.); Nuclcospira Australis (McCoy); Pcntamerus 
Xiistralis (McCoy) ; Cardium Gippslandicum (McCoy); Ortho - 
crras ( cgcloceras ) Z6&g(Sow.^s O.bullatam (Sow.) : O.capillosum 
(Par.); 0. Linear e (Munst.); 0 . Striato-punctatum (Munst.). 
The general character of the Upper Silurian country is very 
mountainous, though a great deal of it, especially around Mel- 
bourne, is only moderately hilly or slightly undulating. 
The crest of the Main Divide, from Mount Arnold to the heads 
of the Barkly, a western branch of the Macalister, maintains an 
average elevation of over 4,000 feet, and consists, as do most of 
the branch range systems on either side, entirely of Upper Silu- 
rian rocks. The descents from the Main Divide and its leading 
spurs into the creeks and rivers are very abrupt, and sometimes 
precipitous ; a very dense and luxuriant vegetation, consisting of 
large Eucalvpts, the various scrubs, and tree ferns, is found 
wherever the depth of surface soil and rubble and the climatic 
conditions are favorable, especially on the south side of the Main 
Divide, in the heads of the Yarra, the La Trobe, the Tanjil, and 
the Thomson Livers.. 
