276 Transactions. 



within the New Zealand region would be more fatal to the northern 

 species, which, owing to the limited extent of the land, would have no 

 warmer littoral waters to which to migrate, than to the southern species, 

 which would have a large extent of northern coast-line to which they could 

 retire as the climate became cooler. This consideration supports the belief 

 that the small percentage of Recent species in the Pakaurangi beds does 

 not indicate a greater geological age than that of the beds at Wharekuri 

 and of Otiake in North Otago. Actually, as explained in an earlier paper, 

 these Pakaurangi beds succeed the white mudstones conformably, and these 

 mudstones merge into the hydraulic limestones in their lower members. 

 The hydraulic limestone is believed to rest conformably on the greensands, 

 which in certain neighbouring localities contain an Upper Senonian fauna. 

 This fauna includes the ammonoid genera Kossmaticeras, Phylloceras, 

 Lytoceras, and Baculites, as well as the gasteropods Amberleya, Cinulids, 

 and the lamellibranchs Malletia, Panojje, and Inoceramus, amongst several 

 others. It is hoped that this fauna, w T hich has been found at Batley and 

 at Bull's Point, both within a few miles of Pakaurangi Point, may be fully 

 described in the next volume of the Transactions. 



There are at Pahi, some five miles distant, some greensands lying 

 beneath the " hydraulic limestones." In these sediments there are a large 

 number of species of fossil Mollusca, but the shells are in a very poor state 

 of preservation, and no attempt has been made of recent years to classify 

 them. It is, however, the case that the species are mainly, if not entirely, 

 of Cainozoic types, and the horizon is certainly lower than that of the 

 Pakaurangi Point beds. Thus stratigraphically there is not any definite 

 indication of the age of the Pakaurangi beds. There are certainly Upper 

 Senonian beds at about 1,000 ft. below them, and the intervening strata 

 are partly extremely fine mudstones and Globigerina oozes with much 

 diatomaceous and radiolarian matter. 



Palaeontologically also the exact age of the Pakaurangi beds is not 

 precisely indicated. The percentage of Recent species does not give a 

 satisfactory basis for a comparison with European horizons. The isolation 

 of New Zealand and the relatively rare arrival of species from outside the 

 New Zealand area make it probable that species would survive for a much 

 longer time here than on coast-lines where there was more competition 

 from newly arrived species. It is probable that a fauna in New Zealand 

 with 20 per cent, of Recent species would have a much greater antiquity 

 than a fauna with a similar percentage of Recent species in Europe or 

 America. 



The actual genera that have, been collected do not appear to indicate 

 any precise Tertiary age. Exilia, Gilbertia, and other genera from the 

 lowest Tertiary beds of the South Island have not been collected here. 

 Fulgoraria has not been found, and Chione is poorly represented. But 

 such facts appear to depend upon station rather than age. Relative strati- 

 graphical position with respect to beds deposited in water of similar depth 

 in other parts of New Zealand would suggest an age rather younger than 

 that of Wharekuri and Otiake, and such a position would generally agree 

 with the palaeontological evidence . On the whole, I am inclined to correlate 

 the beds with those of All Day Bay — that is, next above the Oamaru 

 limestone. 



As the work of collecting, classifying, and describing the Tertiary 

 Mollusca gradually proceeds the number of species becomes much larger, 

 and the fact emerges that there have been very few generic additions to 



