Makshall and Murdoch. — -Tertiary Rocks necn- Wangamii. 125 



*Melina zealandica (Sut.) 

 Musculus impacta (Herm.) 

 Mi/tilus maorianus (Iredale) 

 Natica australis (Hutt.) 



*Natica ovata (Hutt.) 



* Natica sagena (Sut.) 

 Natica zelandica (Q. & G.) 

 Nicculana fastidiosa (A. Ad.) 

 Odostomia aff. hemhix (Sut.) 



*Olivella neozelanica (Hutt.) 

 Ostrea angasi (Sow.) 



*Ostrea ingens (Zittel) 

 Panope zelandica (Q. & G.) 



*Paphia curta (Hutt.) 

 Pecten convexus (Q. & G.) 



*Pecten semiplicatus (Hutt.) 



*Pecten triphooki (Zittel) 

 Pecten zelandiae (Gray) 



^PJialium fibratum (Marshall and 

 Murdoch) 

 Profocardia pidchella (Gray) 

 Psammobia lineolata (Gray) 

 Siphonalia mandarina (Duclos) 



*Sip)honalia subnodosa (Hutt.) 

 Soletellina nitida (Gray) 



*Struthiolaria canaliculata (Zittel) 



*Stri(tJiiolaria zelandica (Marshall and 

 Murdoch) 

 Turritella rosea (Q. & G.) 

 Turritella symnpetrica (Hutt.) 

 Venericardia difficilis (Desh.) 

 Venericardia lutea (Hutt.) 



*Voluta turrita (Sut.) 



* Valuta morgani (Marshall and Mur- 

 doch) 

 Zenatia acinaces (Q. & G.) 



This list contains seventy-two species, of which 61 per cent, are Recent. 



The remarks that have been made about the occurrence of large shells 

 in the strata at Nukumaru apply with even greater force to these beds, 

 for there are these additional extinct species of large dimensions : Cardium 

 spatiosum, Paphia curta, Ostrea ingens, Pecten triphooki, Dentalium soliduni, 

 Natica sagena, Natica ovata, and Crassatellites obesus. The appearance of 

 the large Phalium fibratum adds to the effect. It is hard to resist the 

 opinion that either the climate of the country as a whole was more genial 

 or that the region was a sea-floor that was washed by a warmer current 

 when the sediment was deposited. The latter alternative, however, is an 

 improbable ■ explanation, because the nature of the sediment is essentially 

 the same at Waipipi as it is in the highest of the Castlecliff beds. It thus 

 becomes probable that there was a reduction in the temperature of the 

 New Zealand area which extended over a considerable interval of time. 

 This gradual cooling of the climate continued throughout the lapse of time 

 between the deposition of the Waipipi beds and of the upper beds at 

 Nukumaru. In an earlier portion of this paper this interval of time is 

 stated as possibly as much as 300,000 years. 



The general results of this examination of the fossils on the coast-line 

 between Castlecliff and Waipipi thus show clearly that as lower and 

 lower strata are inspected the percentage of extinct species of mollusca 

 becomes greater and greater. This increase of extinct species could be 

 due mainly to three different conditions. 



(1.) The mere increase in age as the lower beds are reached might in 

 itself account for it, because as time proceeds various species become 

 outclassed in the struggle for existence that is always in progress. The 

 many slight changes in food-supply, ocean currents, and accompanying 

 variations of temperature may be as potent in this direction as the mere 

 lapse of time and the consequent change of vital energy of the different 

 species. 



(2.) The migration of additional species to the district or to the region 

 would, of course, have a similar effect; but in our opinion our collections 

 of the mollusca afford no evidence of this. On the contrary, as one of us 

 (Marshall) has frequently pointed out before, the present moUuscan fauna 

 of New Zealand seems rather to be a remnant of a more extensive fauna 



