172 Transactions. — Geology. 



Miocene and Pliocene genera of Mollusca appeared first in 

 Australia, and afterwards in New Zealand, showing that part 

 of our Tertiary fauna reached us from Australia, and not 

 from an antarctic continent. Nevertheless, out of the 268 

 species of Mollusca known from the Oamaru and Pareora 

 series, only thirty-one, or 11^ per cent., are found in Austra- 

 lia, which is a less percentage than exists at the present time. 

 So that our fauna was, even in the Miocene, very different 

 from that of Australia. What is perhaps still more noticeable 

 is that no less than thirteen species of our Miocene Mollusca 

 are also found fossil in the Tertiary rocks of Patagonia, and 

 of these only tw^o are known in Australia. This shows some 

 connection with Patagonia in which Australia did not share. 



Another important fact connected with the Miocene period 

 is the great outburst of volcanic energy in the North Island. 

 In the South Island the only eruptive rocks we know to be of 

 this age are the dolerites of Moeraki and Mount Charles in 

 Otago, and those of Timaru and Mount Cookson near Waiau ; 

 to which may perhaps be added Mount Herbert in Banks 

 Peninsula. These w^ere the last expiring efforts of vulcanism 

 in the South, and its energy now shifted to the North. The 

 andesites of the Thames Goldfields,''' as well as those of 

 Whangarei Heads, Kaipara, and the Great Barrier Island, as 

 also the trachytes of Hicks Bay,f date from the early part of 

 this period. And as pumice is found in rocks of Miocene age 

 at Hawke's Bay]: it seems probable that part of the rhyolites 

 and andesites which form the plateau extending from the 

 southern side of Lake Taupo through Patatere to Te Aroha 

 are of Lower Miocene age. At a slightly later date came the 

 rhyolites forming the cliffs round Lake Taupo, which ai'e 

 remarkable for containing small crystals of hypersthene, by 

 the presence of which the pumice of Taupo can be dis- 

 tinguished from that found elsewhere. 



Pliocene Period. 



The "Wanganui series contains a number of marine fossils, 

 of which from 75 to 93 per cent, of the shells and about 

 76 per cent, of the Polyzoa belong to still livmg species, 

 so that we can safely consider it to be newer Pliocene. It 

 hes unconformably on Miocene rocks at Napier, and it is 

 doubtful whether we have in New Zealand any marine beds 

 belonging to the older Pliocene. The Wanganui series is 

 known only in the southern half of the North Island, from 

 Patea and Wanganui on Cook Strait to the northern part of 



" Report Aust. Assoc. Adv. Science, vol. i., p. 2.53; Sydney, 1887 

 t Cox, Reports Geol. Explor. for 1876-77, p. 112 

 \ Hill, Trans. N.Z. Inst., vol. xx., p. 304. 



