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



Victoria, which, according to the late Sir E. Daintree, contain 

 " strata, mainly composed of fine mud, dotted thoughout with 

 various-sized, generally rounded, pebbles, and those pebbles mostly 

 unknown in the vicinity, and some not yet seen in place so far as 

 the Geological Survey has extended a minute examination 1 ; " further 

 on he says that " blocks of granite, in some instances over a ton 

 in weight, are found imbedded in a matrix of soft mud 2 ;" and in 

 the last progress report by the Secretary for Mines in Victoria, Mr. 

 Murray states, on the authority of the late Sir E. Daintree, that 

 some of these granite boulders resemble no granite that occurs as 

 a rock-mass nearer than Queensland. 3 



This contrast in the nature of the evidence of glacial action shows 

 that, if this form of argument is at all admissible, it is with the 

 Lower Carboniferous marine, rather than with the Hawkesbury 

 glacial beds that we must associate those of Bacchus Marsh. 



Nor can palaeontology be said to support Dr. Feistmantel's hypo- 

 thesis ; for Gangamopteris, the only genus of plants known from 

 the Bacchus Marsh beds, is found neither in the plant-bearing beds, 

 interstratified in the Lower Carboniferous marine group, nor in the 

 Hawkesbury group. It has, however, been found in the intervening 

 Newcastle group, and one species is identical with a Bacchus Marsh 

 form ; moreover, the only other species of Gangamopteris in the 

 Newcastle beds is, according to Dr. Feistmantel, closely allied to one 

 of the Bacchus Marsh species. This fossil evidence would by many 

 be regarded as sufficient to prove the contemporaneity of the Bacchus 

 Marsh and Newcastle groups ; but the beds of the latter show no 

 trace of glacial action, so that the former cannot be referred to that 

 age in face of the existence of evidence of glacial action in the beds 

 above and below. A reference to Dr. Blanford's address will show 

 that whereas a very close relationship exists between the floras of 

 the Newcastle and Lower Coal-measures, there is next to none between 

 those of the former and the Hawkesbury Sandstones ; and I. may add 

 that the stratigraphy of the beds appears to point to the same con- 

 clusion as the palaeontology ; so that, as the choice lies between the 

 two, it is again rather with the Lower Carboniferous marine than 

 with the Hawkesbury group that we must associate the Bacchus 

 Marsh beds. 



The Bacchus Marsh beds are not known to occur in conformable 

 contact with any other group ; but there is a large tract of country 

 covered by an upper group of the same series, which is characterized 

 by the occurrence of Tmiiopteris Daintreei, a form which occurs in 

 New South Wales in the beds overlying the Hawkesbury and Wiana- 

 matta groups. Owing to the large area covered by more recent lava 

 flows, the exact relation of the two groups is unknown ; but there can 

 be little doubt that they are unconformable, for the Bacchus Marsh 

 beds are overlapped by the Tceniopteris beds, which rest unconform- 



1 Geological Survey, Report on the Geology of the District of Dalian, by Richard 

 Daintree, p. 10, Melbourne, 1866. 



2 Ibid., p. 10. 



3 Geological Survey, Progress Report by the Secretary for Mines, p. 80, Melbourne, 

 1881. 



