Notes on Miocene Strata at Jemmy's Point. G3 



been called in question. This has arisen, I think, from a 

 misconception of the limits of the method. If it be true 

 that species have gradually changed, or that they have been 

 gradually introduced into an area — which no one doubts — 

 then it must be true that, in each epoch, the nearer we 

 approach to the present time, the nearer must be the 

 resemblance between the fauna of the epoch and that of 

 the present time. Indeed, the same holds good if, instead 

 of assuming gradual change, we assume that the ancient 

 fauna was altered by successive migrations into the area ; 

 for it is evident that the percentage test would be of great 

 value here in ascertaining the relative ages of the various 

 migrations ; for each migration would bring many species 

 similar to or allied to those now living, consequently the 

 percentage system is of the greatest importance in testing 

 the relative ages of any two sets of beds belonging to the 

 same biological province. But it does not follow that this 

 method can be trusted for correlating with accuracy sets of 

 beds in widely distant areas. On the contrary, different 

 districts have undergone different physical changes, and we 

 have therefore every reason to suppose that alterations in 

 floras and faunas would ]5roceed with unequal rapidity in 

 different parts of the world."* 



It was stated above that out of 1 02 species of Mollusca in 

 the Jemmy's Point beds, IG are living, which is within a 

 fraction of 1 G per cent., and the beds may therefore be 

 confidently referred to the Miocene period. Many more 

 species will, I hope, yet be obtained from the strata ; but, 

 judging from tlie similarity of the gatherings by the 

 members of our party, as well as by Mr. Gregson, this 

 proportion is not likely to be materially altered. 



Only one other deposit in Victoria has, so far, been 

 definitely classed as Miocene, viz., the upper beds at Muddy 

 Creek. In South Australia, the oyster beds of the Mun-ay 

 cliffs and elsewhere, are also referred to the same epoch. 

 In both of these, the percentage of recent shells, as calculated 

 from the described forms, is not more than half that given 

 for the Jemmy's Point fossils ; but with regard to the Muddy 

 Creek fauna, when the work of naming all the species 

 obtained is completed, the proportion will, I think, be 

 slightly raised. The tertiaries of Australia are perhaps not 



* "The Wanganui System," by Captain F. W. Hiitton, F.G.S., " Trans- 

 actions New Zealand Institute " 1885. 



