217 



geological horizon, pointing to a shallowing of tlie sea bottom, 

 which is indicated not only by the relatively larger numbers of 

 shallow-water species in the upper beds, but these are pro- 

 portionally more numerous and better developed as individuals.""^ 

 Quite a large area in the south-west of Victoria, including 

 nearly the whole of the county of Follett and a portion of 

 Normanby, is occupied by strata which liave been tentatively 

 included in the Miocene. The deposit is of moderate thickness, 

 nowhere perhaps more than from 20 to 30 feet through, and 

 from the prevalence of a species of oyster in it has been named 

 Ostrea-limestone. This, together with two other common fossils 

 accompanying it, belong to living species ; but besides these 

 there are casts of other shells, which can only be doubtfully 

 determined. The three living species referred to do not occur in 

 the Miocene strata just described, and the Ostrea-limestone is 

 classified as Miocene chiefly on stratigraphical grounds. It over- 

 lies the Eocene calciferous rock, and was certainly deposited 

 before the Pliocene beds to be mentioned presently At Portland 

 its junction with the Eocene rock is very plainly seen, a pebble 

 band, a few inches tliick, separating the two. Fine sections of 

 the Ostrea-limestone are visible on the Glenelg clift's at Dart- 

 moor, and the same rock has been traced through Strathdownie, 

 and on to the Dismal Svvamp, just across the border in South 

 Australia. Lithologically, the strata consist of flaggy limestones 

 showing much false bedding. When disintegrated, they form 

 immense beds of sand, which become tlie leading feature of the 

 country where the formation prevails. Where the rock is 

 exposed it is often smooth, and breaks up into flat cakes of 

 limestone, which are so thickly strewn over the ground in places 

 as to make it difficult to drive over the roads. Possibly these 

 l^locks of stone may sometimes cc^nsist of travertine, formed by 

 the re-deposition of carbonate of lime, which has flrst been 

 dissolved out by water from the original rock ; that this is not 

 the case for all of them is certain, as they frequently contain 

 fossil shells. 



NEWER PLIOCENE. 



The only marine Pliocene outcrop known in Victoria is that 

 on the Glenelg River, at Limestone Creek, described a few years 

 ago.f It rests upon tlie jDolyzoal rock, and from its position is 

 evidently of later date than the Ostrea-limestone on the top of 

 the river cliffs. The proportion of living to extinct species of 

 mollusca present amounts to more than 80 per cent., so that it 

 must be referred to the latter part of the Pliocene period. 



* Roy. Soc. S. Alls., vol. XII. 



+Roy. Soc. of Victoria, vol. XXIII., 1887 ; and Trans. Aust. Assoc. 

 Adv. of Science, Melb., 1890. 



