Marshall. — Relations between Cretaceous and Tertiary Socks. 119 



though, other authorities have considered the two formations thus classified 

 to be conformable. 



The rocks in South America described as Cretaceous contain a number 

 of fossils which belong to genera which are well represented in the Miocene 

 rocks of the neighbourhood. 



The Cretaceous found in South America thus contains a distinct Miocene 

 element, which may be regarded as ancestral of the Miocene fauna. 



Cephalopods are either very scarce or are absent from these Cretaceous 

 strata. 



The strata at Wangaloa, Hampden, and Brighton, admitted to be near 

 the base of the New Zealand younger series of rocks, together contain species 

 of Mollusca similar to those which have caused the Chico, Quiriquina, and 

 some Patagonian strata to be classed as Senonian. The Wangaloa beds 

 in particular contain also a large number of extinct species of Mollusca 

 belonging usually to genera well represented in the New Zealand Tertiary 

 strata. These species include 50 per cent, of the Wangaloa fauna. There 

 are also at Wangaloa 40 per cent, of species found elsewhere in the Miocene 

 rocks of New Zealand, and of these some 13*5 per cent, are Recent species. 



If these strata are not of Senonian age, they clearly indicate that there 

 were several highly important Cretaceous survivals when the deposition 

 of the Tertiary beds began in New Zealand. 



If they are of Senonian age, they indicate that the Miocene fauna was 

 already partly developed before the close of the Cretaceous. 



At the Selw}ai Rapids, where 'the strata have always been classed as 

 Cretaceous, the distinctly Miocene genus Struthiolaria has now been definitely 

 found. 



The fauna clearly suggests that a palaeontological break between the 

 Cretaceous and the New Zealand Tertiary either does not occur or that it 

 is of little importance. This conclusion agrees with the result previouslv 

 stated, that in the opinion of the author and of several other New Zealand 

 geologists no stratigraphical break has been found between these formations. 



These results appear to agree satisfactorily with those obtained in 

 western California, Chile, Patagonia, the Magellan area, and Seymour Island 

 in Antarctica. 



Postscript. 



The whole question as to whether the fossils and formations referred to 

 in this paper as Miocene are rightly classed in this way is a matter that will 

 probably be much discussed in the future. The classification as Miocene 

 is based almost wholly on the high percentage of Recent species. It would 

 obviously be better to use New Zealand local names for the horizons of the 

 Tertiary rocks of this country. Thus the Wangaloa series might include 

 all those rocks that contain from 5 to 20 per cent, of Recent species, the 

 Waitaki series from 20 to 40 per cent., and the Wanganui series any higher 

 percentage of Recent species. 



