90 Transactions. 



over the period that in Europe elapsed between the Upper Miocene and 

 the Upper Pliocene, though we do not wish to insist upon this correlation. 

 It appears to us that under the peculiar conditions in New Zealand 

 which necessarily resulted from the prolonged isolation of this small land 

 the rate of organic change, so far as it is shown in the marine mollusca, 

 does not give a very satisfactory basis for the correlation of the New 

 Zealand sediments with those of Europe, so far at least as the Tertiary 

 rocks are concerned. 



(2.) Climate : Tf it be accepted that the continuity of the strata in 

 the Wanganui coast is as precise as has been described, it at once becomes 

 evident that climatic conditions in New Zealand have been warm or mild 

 during the whole period of time that was occupied in the deposition of 

 the sediment. It has also been suggested that, this lapse of time is more 

 or less equivalent to the interval between the Upper Miocene and the 

 Upper Pliocene in Europe. Whether this is the case or not, it may be 

 taken as certain that the period called by Hutton the " older Pliocene " 

 is comprehended in this interval. All who have studied New Zealand 

 geology are aware that Hutton was of opinion that the great extension 

 of the glaciers of New Zealand occurred during this Upper Pliocene. We 

 hold that the evidence which we have been able to bring together shows 

 conclusively that the climate of New Zealand during this Upper Pliocene 

 period was at the least as genial as it is now, and that there can have 

 been no glacial extension relative to the present sea-level during that period. 

 There is, on the other hand, much evidence that the warm climate of the 

 early Tertiary has become a good deal colder duriDg the late Tertiary in 

 this country. At least three genera which indicate warm conditions — 

 Mdina, Olivella, and Miltha — have now disappeared. In many other 

 genera species of large size have been replaced by others of much smaller 

 dimensions. Large species of Melina are at present restricted to the warmer 

 tropical waters, and it may well be held that Olivella and the large species 

 of Miltha indicate the prevalence of warm climatic conditions. This con- 

 clusion is enforced by the occurrence of large species of Cardium, Cytherea, 

 Pecten, Ostrea, Paphia, Natica, and Dentalium. It becomes evident that 

 climatic conditions in New Zealand between the Upper Pliocene and the 

 Upper Miocene, so far as these periods can be judged by the nature of the 

 marine mollusca now exposed on the cliffs of the north coast of Cook 

 Strait, were never colder than now, and during the greater part of that 

 time they were a great deal more genial. There is also evidence that 

 during at least the earlier portion of this interval the climate was a great 

 deal warmer than it is at the present day. 



(3.) Change in fauna : AVe regard it as a fact that during the long period 

 of time that is represented by these sediments there has been no sudden 

 appearance of a new fauna. Everywhere the fauna contained in each 

 separate stratum may reasonably be regarded as the lineal descendant of 

 that in lower strata, though in each stratum there are perhaps a few 

 species or genera that are found sparingly elsewhere. In no case, how- 

 ever, is there such a change as to justify the opinion that a foreign element 

 has been introduced into the previous fauna. This idea of the continuity 

 of the marine molluscan fauna of the younger Tertiary rocks of New 

 Zealand may be carried a little further, for it is a fact that the fauna 

 of the highest beds that are exposed differs but slightly from the marine 

 molluscan fauna of the present day. It is certainly a fact that no 

 additional foreign element distinguishes the Recent fauna from that which 

 is contained in the Castlecliff beds. 



