56 



Creek are. Their percentage composition is not uniform, but 

 lime, alumina, iron, silica, and carbon dioxide, were found in all, 

 though in varying proportions in different samples analysed. They 

 differ from the Muddy Creek nodules in containing a smaller 

 amount of iron and no phosphoric acid. Although the pebble 

 bands of Muddy Creek and Portland Bay are thus in some res- 

 pects unlike, they, nevertheless, mark a distinct break in the suc- 

 cession of the strata at both places. 



The most abundant fossil in the Ostrea limestone is Ostrea 

 arenicola (Tate), which is closely allied to 0. Angasi, a living 

 species. In addition, I have collected the following, chiefly from 

 the exposures of the strata on the Glenelg cliffs : — Pecten nieridio- 

 nalis (Tate), Mytilus chorus (Molina), Chthalamus stellatus 

 (Poll), Placunanomia lone (Gray), Zenatiopsis angustata (Tate), 

 of which all but the last are living species. The Ostrea lime- 

 stone must either belong to the late miocene or early pliocene 

 period, probably the latter, the next older formation being, I 

 think, the upper Muddy Creek beds. 



III. Associated Rocks axd Thickness of Strata. 



As mentioned in the introduction, we do not know what for- 

 mation the great body of the tertiaries in south-western Victoria 

 rests upon. Even at Muddy Creek, which cannot be far from 

 their northern boundary, the fossiliferous beds have not been 

 pierced, and what underlies them has yet to be discovered. A 

 few years ago, two energetic fossil hunters determined to solve 

 this question iDy sinking a shaft in the bed of the creek. Un- 

 fortunately, their geological knowledge was not equal to their 

 enthusiasm, as they chose a spot quite near the top of the upper 

 beds, so that though they went down a good distance, they never 

 even reached the lower beds, many feet of which are exposed in 

 natural section on the banks of the stream, a few chains farther 

 down. I would venture to suggest that the work of piercing 

 such important beds as these should be undertaken by the Survey 

 Department of Victoria. Whether boring operations here, and 

 in the neighbourhood, would be likely to lead to discoveries, Avhich 

 could be turned to profitable use or not, I cannot say, but the 

 scientific value of the information gained would be great. I had 

 some grounds for thinking, at one time, that the expense of sink- 

 ing a shaft would be defrayed by the Ballarat School of Mines, 

 a proposal to that effect having been at first very favourably 

 received. In the end, however, other counsels prevailed, and it 

 was decided that no funds w^ere available for such a purpose. 



It is true that, at many places on the Grange Burn, certain 

 rocks appear just beneath the tertiaries, but they are of igneous 

 origin, and have penetrated through some earlier sedimentary 



