Nomenclature of Geological Age. 161 



enough, but Sir James Hector's local term fully meets all 

 requirements, even accepting the stratigraphical and palaeonto- 

 logical interpretation to be the correct one. If, however, any 

 mistake has been made in either respect, what becomes of 

 Cretaceo-tertiary ? If a time word must be used to give further 

 information, it should not be difficult to fix on a usual one, 

 tentatively at least, with a full explanation of local peculiarities 

 or characteristics. 



This method should recommend itself, and at the same time 

 prevent much useless theorising. 



Mr. J. E. Marr^ expresses clearly a valuable point which may 

 have some bearing here, he says, " There is an unconformity 

 between the Cretaceous and Eocene beds of England, which is 

 accompanied by a palaeontological break, but this break is more 

 pronounced owing to difference of physical conditions, for we 

 find abundance of gastropods in the Lower Tertiary beds, and a 

 rarity of these shells at the top of the chalk of England, though 

 where physical conditions were favourable for the growth of 

 gastropods, their shells are found in the higher strata of chalk age, 

 and the palaeontological break is not so apparent." 



In the Mesozoic the first departure to note is Super- or Supra- 

 Cretaceous used for what is generally known as Desert Sandstone 

 in Central Australia and Queensland. The first use of this term 

 appears to have been made by Mr. H. Y. L. Brown as Super- 

 Cretaceous,- but as Messrs. Jack and Etheridge say, Mr. Brown 

 does not distinctly aver that the " Super-Cretaceous " rocks 

 described by him lie unconformably on the Cretaceous. Professor 

 Tate and Mr. J. A. Watt in their report on the General Geology 

 of the Horn Expedition^ use Supra-Cretaceous and state, " No 

 evidence of unconformability between Upper Cretaceous and 

 Desert Sandstone was observable between Oodnadatta and the 

 northern confines of the Cretaceous area, though there is some 

 reason for the opinion the latter ovex'laps the former." 



Messrs. Jack and Etheridge in their Geology of Queens- 

 land* clearly regard the Desert Sandstone as most conveniently 



1 Principles of Stratigraphical Geology, 1898, p. 65. 



2 Report of Government Geologist, Adelaide, 1883. 



3 Horn Scientific Expedition to Central Australia, Part iii.. Geology, p. 65. 



4 Geology and Palaeontologj' of Queensland and New Guinea, pp. 1, 3, and 510. 



11 



