in South- Western Victoria. 241 



to speak briefly of the more ancient strata, through which 

 the Glenelg has carved out the southern part of its course — 

 viz., the coralline limestone. The thickness of this is 

 unknown, but that it is very great is certain, from the fact 

 of there being no outcrop of a different rock for many miles 

 in any direction. It underlies the bed of the river from its 

 mouth almost as far as Casterton, where mesozoic and 

 Silurian rocks appear. Its fossils are numerous, and fairly 

 well known; from their evidence the whole formation is 

 considered to be of miocene age. At the Devil's Den is a 

 massive cliff, 130 feet high, composed of this rock, and 

 covered by a band of oyster shells, as is usual with the strata 

 generally. Near it, similar though smaller cliffs exist 

 towards the summit of the banks, while farther down the 

 river, the limestone is continuous to the water's edge. At 

 Ascot Heath, about ten miles south from Limestone Creek, 

 the oyster beds at the top of the bank are as much as 8 or 

 10 feet thick, the coralline rock with its characteristic fossils 

 lying immediately underneath. The oysters found on the 

 Glenelg terraces are of the same species as those in the cliffs 

 above; but it does not necessarily follow that they are 

 derived from this source, their great abundance in the 

 Bankivia beds being against such a theory^ and we can only 

 conclude that they were common to both formations. The 

 small variety of fossils in the Ostrea limestone renders the 

 determination of its age difficult, but it is undoubtedly much 

 less ancient than the coralline strata, as amongst the few 

 fossils which have been obtained from it, several are identical 

 with living forms, while, as is well known, a large proportion 

 of those in the coralline belong to extinct species. 



Again, Entalis annulatum, CucuUaea Corioensis, &;c. 

 are frequent shells in the coralline formation, and the 

 possibility of their derivation from it must be admitted. 

 There are_, however, certain considerations which induce 

 me to take an opposite view, and to regard them also 

 as part of the original deposit. Five of the eight extinct 

 shells are very rare, being represented in my collection by 

 solitary examples only, while specimens of most other 

 species are tolerably numerous. With the exception of 

 Gryphaea tarda, they are all found in some part of the 

 Muddy Creek series, which is usually considered as equivalent 

 to the coralline. There are altogether twelve species com- 

 mon to the Muddy Creek and Bankivia beds, of which five 

 are recent as well as fossil, and as these five old tertiary 



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