Marshall and Murdoch. — Tertiary Bocks near Ha-wera. 93 



to justify a consideration of the indications that they offer regarding the 

 relations of New Zealand to other land areas in past time. It is evident 

 that an accurate knowledge of the Recent fauna is of special importance 

 when one is dealing with the main facts of the Tertiary geology of this 

 country. Sir James Hector some forty years ago said, : ' An accurate 

 knowledge of the affinities and distribution of the Recent shells of New 

 Zealand is a very necessary element in the geological survey of this 

 country."* The application of this principle is as essential now as it was 

 then. Hutton, in the Introduction of his Manual of 1880,f states that the 

 better the fauna of New Zealand becomes known, the more prominently 

 does it stand out as distinct from that of any other country, and this is 

 particularly the case with its shells. Again, in his Introduction to the Index 

 Faunae Novae Zealandiac,% he summarizes the elements of our fauna, points 

 out the affinities with other faunal regions, and applies the test of geological 

 evidence to indicate the time of their appearance in our area and the 

 probable source from which they were derived. Hutton's review of our 

 fauna, however much we may differ from many of his conclusions, does 

 most distinctly emphasize its ancient character and the long period of 

 isolation that is needed to account for many of its peculiarities. 



Palaeontology in New Zealand has within recent years made a very 

 considerable advance, more especially in our knowledge of the earlier Tertiary 

 faunas, though there is still a rich field for further research. Enough, 

 however, is now known to simplify many of the difficult problems that 

 beset Hutton in 1904. 



At the first view it may appear that our molluscan fauna contains a 

 very considerable Australian element. According to Suter§ there are about 

 140 species common to both, a number that is about equal to one-eighth 

 of the total species that he records. Recent investigations show that many 

 of his determinations cannot be upheld, that others are very doubtful, and 

 others again, such as Tonna. are really varietal and not strictly identical 

 with the Australian species. But, admitting that there is a considerable 

 number of species common to both, including the Cymatiidae, a group of 

 large shells every New Zealand species of which occurs in Australian waters, 

 it is not necessary to imagine a bridge across the Tasman Sea, or even to 

 demand a close approach of the two land areas. The larvae of the marine 

 mollusca are free-swimming creatures. In some species this stage in their 

 life-history is brief, but in others it is of some length. Myriads of them 

 are, of course, carried out to sea and perish, but when aided by ocean cur- 

 rents and other favourable conditions they are able to travel long distances. 

 The southern portion of Australia, or at least Tasmania, may be said to 

 he in the region of the -i roaring forties," and the southern portion of the 

 Tasman Sea is constantly swept for a portion of the year by hard and 

 prolonged westerly gales, and with this aid from time to time some of the 

 larvae would be certain to reach our shores. We might reasonably expect 

 a larger and more important Australian element in our molluscan fauna 

 than we actually have. It is obvious that very few of the species that 

 survived the journey across the Tasman Sea would succeed in establishing 

 themselves in the face of a new set of natural enemies, as well as changes 

 in climatic and physical conditions. If the accession to our fauna had been 



* In Hutton's Manual of the New Zealand Mollusca, Preface, p. iii, 1880. 



t Ibid., p. ii. 



I F. W. Hutton, Index Faunae Novae Zealandiae, Introduction pp. 13-19, 1904. 



§ H. Sttter, Manual of the New Zealand Mollusca, pp. v, vi, 1913. 



