H. D. Oldham — On Homotaxis and Contemporaneity . 297 



fauna, and physical aspect, all leave little room for doubt that they 

 are of the same age. Beds of similar aspect have been described by 

 Mr. R. L. Jack, in Queensland. These beds — also of marine origin, 

 and indicating the presence of ice floating in the sea by which they 

 were deposited, 1 contain 22 species of fossils, so far as the fauna is 

 known, of which 15 are also found in the marine beds of New South 

 Wales, and only seven have not been found to the south. 



As the case stands, there are in Australia two sets of beds, both 

 of which indicate the presence of floating-ice in the water in which 

 they were deposited. One of these, the Bacchus Marsh group, is 

 shown by its plant fossils to be homotaxial with the Talchir group 

 of India ; the other has yielded a marine fauna of Lower Carboniferous 

 facies, as judged by European standards, and a limited flora which, 

 however, does not show any direct relation to that of the Bacchus 

 Marsh beds. 



I am not aware of any published attempt to correlate the Bacchus 

 Marsh beds with a definite horizon in New South Wales before Dr. 

 Feistmantel in 1880 gave it as his opinion that they were the 

 equivalents of the Hawkesbury Sandstones. This opinion, so far 

 as I can glean from his published writings, was based on the so- 

 called Lower Mesozoic facies of the Bacchus Marsh flora, and was 

 supposed to be confirmed by Mr. C. S. Wilkinson's discovery of 

 glacial action in the Hawkesbury Sandstones. Mr. Wilkinson thus 

 describes this evidence 2 — " In the sections exposed in the quarries 

 at Fort Macquarrie, Woolloomooloo, Flagstaff Hill and other places, 

 may be seen angular boulders of shale 3 of all sizes up to 20 feet in 

 diameter, imbedded in the sandstone in a most confused manner, 

 some of them standing on end as regards their stratification, and 

 others inclined at all angles. They contain the same fossil plants 

 that are found in the beds of shale from which they have evidently 

 been derived. These angular boulders occur nearly always imme- 

 diately above the shale-beds, and are mixed with very rounded 

 pebbles of quartz ; they are sometimes slightly curved as though 

 they had been bent while in a semiplastic condition, and the shale- 

 beds occasionally terminate abruptly as though broken off." 



It is difficult, if not impossible, to account for these appearances, 

 except by the action of ice in some form or other ; the angular form 

 of the fragments of shale shows that in some manner they must 

 have been indurated before disturbance, and it is impossible to 

 account for this induration of what must then have been recently 

 deposited mud except by the freezing of the interstitial water. This 

 supposition would accord with the general nature of the evidence, 

 which indicates the action of ground-ice, such as is formed during 

 the severe winters of North America, rather than the presence of 

 large masses of floating-ice ; and hence does not necessarily indicate 

 so severe a climate as that afforded by the Bacchus Marsh beds of 



1 Eeport on the BowenEiver Coal-field, by B. L. Jack, Esq.,F.G.S., Brisbane, 1879. 



2 Notes on the occurrence of a remarkable boulder in the Hawkesbury Eocks, Trans. 

 Eoy. Soc. N. S. W. xiii. 105 (1884). 



3 Which is interbedded with the sandstones. 



