205 



Muddy Creek (hiuer heels):* Portland, Gleiielg River, and 

 Apsley. t 



1. Mitchell River, Geelong, Muddy Creek,. Arc. 



The sections of the Mitchell river-cliffs are interesting, because 

 both the calciferous rock and the arenaceous beds are found in close 

 proximity, the one showing principally casts in limestone of fossil 

 shells, and the other yielding numerous sjjecies of univalves and 

 bivalves in an excellent state of preservation. That the 

 difference is simply one of sedimentation and not of geological 

 age is here abundantly plain. Certainly every species recog- 

 nisable in the hard rock has also been collected in the underlying- 

 softer beds. To the south-east, on the margin of the Gippsland 

 Lakes, and elsewhere in the vicinity, the true Miocence makes its 

 appearance, resting against the basal part of the eroded escarp- 

 ment of the forementioned Eocene cliffs. 



Diagram sections, showing very clearly the stratigraphical 

 relations of these two sets of strata, are given by Mr. Howitt in 

 his Reports. 



In comparing the results of their observations in the Geeloxg 

 District with those made by us at Muddy Creek and on the 

 Murray Clilis, Messrs. Hall and Pritchard remark : — " The evid- 

 ence we have adduced shows that in this locality as well, the 

 sequence of the beds, as might have been expected, is similar. 

 The deposit at Orphanage Hill, and consequently its extension 

 up the valley of the river, is usually spoken of as Oligocene, 

 though coloured Miocene in the quarter sheet ; while the Waurn 

 Ponds rock, which, like the Batesford limestone, is a true poly- 

 zoal rock, is called Miocene. This is, however, a reversal of the 

 true sequence, for the limestone is undoubtedly the underlying 

 member of the series." 



Regarding the Muddy Creek lower beds but little has to be 

 added to what has been already recorded. The number of species 

 has been slightly increased, and though much yet remains to be 

 done, progress has been made in the systematic revision of the 

 gasterojDoda. Out of a total of 725 species of all classes from 

 the two well-marked zones at Muddy Creek, 511 have been 

 definitely traced to the lower beds. Of these, from six to eight 

 still survive, and the percentage of recent to extinct forms is 

 thus about one and a half. Independently of the small per- 

 centage of living species, the facies of the fauna is strikingly 

 Eocene, and is in marked contrast to that of the overlying 

 Miocene beds. It is significant, that of the total number of 

 species recorded from the lower zone, only about 5 per cent, pass 



* Roy. Soc. of S.A., vol. XI. 



t Trans Austr. Assoc. Adv. of Science, Melb., 1890. 



