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Volume 53, 1921
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Art. XII.—Tertiary Rocks near Hawera.

[Read before the Wanganui Philosophical Society, 25th October, 1920; received by Editor, 31st December, 1920; issued separately, 27th June, 1921.]

In the last volume of the Transactions of the New Zealand Institute we published lists of fossils from various localities on the coast-line to the north-west of Wanganui. During the past year we have been able to make collections on the beach at Hawera, some twenty miles farther along the coast in the north-west direction. Throughout this distance the rocks are of the same general nature as they are near Wanganui—in other words, micaceous sands and clays (the papa rock). If anything, the material is rather more sandy on the average than it is farther south. There is perhaps rather less mica, and black grains are rather more numerous among the quartz-grains. The strike of the strata changes a good deal. As stated in our former paper, the strike between Castlecliff and Nukumaru is, on the average, 70°. By the time Patea is reached it is as much as 100°, and still farther north, at the mouth of the Tangahoe Stream, on the coast opposite Mokoia, it is 145°. This shows clearly that there is a gradual swing in the strike as one proceeds to the north-west. The dip is always to the south-west and is always slight, and has an average of about 4°.

The direction of the strike and dip as related to that of the coast is such that older and older beds are exposed as one journeys north until the mouth of the Tangahoe is reached. At this point the trend of the coast is parallel to the strike of the strata, and as one goes still farther north younger and younger strata again begin to make their appearance. About 500 ft. of strata separate the lowest horizon three miles north of Waipipi from the horizon at the mouth of the Tangahoe Stream. The Waihi beach

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is five miles to the north of the mouth of the Tangahoe, and the horizon exposed on the beach at that point is about 100 ft. higher than the lowest horizon at the Tangahoe mouth, and is therefore 400 ft. lower than the Waipipi horizon, or, in other words, 4,200 ft. below the highest beds at Castlecliff.

The great regularity of the stiatification which is so noticeable to the south-east of Waipipi is just as noticeable in the strata exposed along the coast-line to the north-west of that place. There is no unconformity as far as our observations went, and there is no evidence of a stratigraphical disconformity. The similarity, too, of the molluscan faunas in the localities that have been mentioned is also so great as to show clearly that there is a palaeontological continuity.

Fossils from Hawera.

  • Ancilla depressa (Sow.)

  • Anomia huttoni Sut.

  • Arca novae-zelandiae E. A. Smith

  • Atrina zelandica (Gray)

  • Calliostoma pellucidum (Val.)

  • Calliostoma selectum (Chemn.)

  • Calyptraea novae-zelandiae var. inflata (Hutt.)

  • *Cardium spatiosum Hutt.

  • *Chione chiloensis Phil.

  • *Chione chiloensis var. truncata Sut.

  • Chione mesodesma (Q. & G.)

  • Chione yatei (Gray)

  • *Crassatellites aff. trailli (Hutt.)

  • *Crepidula gregaria Sow.

  • Crepidula monoxyla (Less.)

  • Cytherea oblonga (Hanley)

  • *Dentalium pareorense Pilsbry and Sharp

  • *Dentalium solidum Hutt.

  • Divaricella cumingi (Ad. & Ang.)

  • Dosinia lambata (Gould)

  • Dosinia subrosea (Gray)

  • *Fulgoraria morgani Marshall and Murdoch

  • *Fulgoraria sp.; not Recent

  • *Fusinus aff. spiralis aff. dentatus (Hutt.)

  • Glycymeris laticostata (Q. & G.)

  • *Glycymeris subglobosa Sut.

  • *Lima waipipiensis Marshall and Murdoch

  • *Lucinida levifoliata Marshall and Murdoch

  • Macoma edgari Iredale

  • Macrocallista multistriata (Sow.)

  • Mactra scalpellum Reeve

  • *Melina zealandica Sut.

  • *Miltha zelandiae Marshall and Murdoch

  • *Natica ovata Hutt.

  • *Natica sagena (Sut.)

  • Nuculana bellula (A. Ad.)

  • *Olivella neozelanica (Hutt.)

  • Ostrea angasi Sow.

  • Ostrea cucullata Born = corrugata Hutt

  • *Ostrea ingens Zitt.

  • Panope zelandica Q. & G.

  • *Paphia curta (Hutt.)

  • *Pecten semiplicatus Hutt.

  • *Pecten triphooki Zitt.

  • Pecten zelandiae Gray

  • *Phalium fibratum Marshall and Murdoch

  • Protocardia pulchella (Gray)

  • Psammobia stangeri Gray

  • *Struthiolaria canaliculata Zitt.

  • *Struthiolaria zelandiae Marshall and Murdoch

  • Struthiolaria aff. papulosa (Mart.)

  • Thais aff. lacunosa (Brug.)

  • Turritella carlottae Watson

  • Turritella rosea Q. & G.

  • Turritella symmetrica Hutt.

  • Venericardia purpurata (Desh.)

  • Venericardia unidentata (Basterot)

  • Verconella dilatata (Q. & G.)

  • Verconella mandarina (Duclos)

  • Verconella nodosa (Mart.)

  • Zenatia acinaces (Q. & G.)

The species marked with an asterisk are extinct. There are sixty-one species in this list, of which twenty-five are extinct: thus the percentage of extinct species in 41.

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Our examination of the coast-line between Wanganui and the Waingongoro has now proceeded far enough to allow us to discuss various geological theories in the light of the facts that have so far been disclosed. We have now traversed the coast-line for nearly the whole distance of fifty miles, and the following opinions appear to us to be well established:—

(1.)

The series of rocks represents a period of continuous marine deposition.

(2.)

The climate during this period of deposition was at no time colder than at the present, but, on the other hand, during the greater part of the time conditions were distinctly more genial.

(3.)

There is no evidence of any sudden addition to the marine molluscan fauna whilst the deposition was in progress.

(1.) The first of these opinions has to be supported from the palaeonto-logical, stratigraphical, and lithological facts that have been observed. From the palaeontological standpoint the evidence at first sight seems to be in favour of a decided break between the faunas of the two extremes—Castlecliff and Whakino. So greatly do the faunas in these two localities differ from one another that any geologist who saw the Castlecliff fauna at one time and that of Whakino—Waihi near Hawera at another, without examining any of the intermediate localities, would unhesitatingly come to the opinion that they represented different geological periods. It is, of course, true that several identical species occur in the two localities; but it is also true that the dominant species in the one locality are either absent from the fauna of the other or are there reduced to an insignificant proportion. Collections that have been made at intervening points, from two of which we have already published lists, show, however, a clear connection between the two divergent faunas. We have found no locality where the change in the faunas is so marked as to prove that there is a break in the palaeontological succession. The locality that we have found to be most suggestive of such a break is at a point three-quarters of a mile to the south of the Nukumaru boat-landing. Here we have found the last specimens of Melina zealandica, Lutraria solida, Cytherea enysi, Lucinida levifoliata, Mesodesma crassa, and Struthiolaria frazeri. These species, however, do not all disappear at the same horizon, but in a thickness of rock that measures about 100 ft. There is also the additional fact that the horizon in which all these species occur contains also as many as 76 per cent. of Recent species, and the fauna is clearly related in the most definite manner to that in the series of rocks that lies above it. For these reasons we do not regard this horizon as indicating in any sense a palaeontological break. On the other hand, there must be a most definite reason for the important faunal change which is so conspicuous at this horizon. It is our belief that this change is due to climatic conditions, or, at any rate, to a most important change in the temperature of the ocean-water which washed these shores at that time. The species that continued to exist after this time were, however, as varied, and indicate a temperature of sea-water at least as high as that of the present Cook Strait. We are inclined to think—though on this point there is room for much divergent opinion—that, on the one hand, the Waipipi series and the Whakino series contain a fauna that is, from the percentage of Recent species, and from the very nature of the fauna, perhaps equivalent to the Upper Miocene of Europe; but since it is probable that in an isolated country like New Zealand faunal change was relatively slow, it is undesirable, at the present time at least, to place much reliance

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on any such correlation. On the other hand, the Castlecliff series contains a fauna with such a high percentage of Recent species that it is in all probability more or less equivalent to the Upper Pliocene of Europe. While we think that the extreme faunas show as great a difference as is indicated by these periods, we also think that, divergent as they are, a complete transition occurs in the strata between them from the one fauna to the other.

This opinion as to the continuity of the rock-series is also strongly supported by stratigraphical evidence, which may be summarized under three heads:—

(a.) We can nowhere find an important stratigraphical break in the line of cliffs, which is almost continuous throughout the distance. There is, of course, a great deal of irregularity in the stratification, due to tidal scour and to current-bedding, but the cause and nature of this is at once apparent. The only place where we have found anything more important is at a locality about two miles and a half to the north of Kai Iwi. In this place, as mentioned in a previous paper, there is clearly an old land-surface, which is indicated by a thin deposit of beach-worn pebbles, a layer of carbonaceous matter, strata penetrated by roots, and borings of littoral mollusca. On the other hand, this structure is not associated with any distinct change in the species of mollusca, and it must, in our opinion, be regarded as due to a merely temporary and local emergence of a coastline that was otherwise undergoing a submergence about as rapid as the accumulation of sediment for a long period of time.

(b.) We have found no sudden change of dip and strike that has extended through a thickness of more than 100 ft. of sediment. Throughout the strata that are exposed on the coast-line the strike and dip are remarkably constant. The strike swings round gradually from 85° at Castlecliff to 125° near Whakino, but, except for a few local variations, there is no sudden change. Perhaps the most marked of these sudden variations is that which occurs at the mouth of the Waipipi Stream, but in a few hundred yards along the beach the normal strike is restored.

(c.) Lithologically the sediments are very similar throughout. In those few localities where there are embedded pebbles they are always fragments of submetamorphic rocks of the nature of greywackes. Where the sediments are of a finer nature they are always bluish-grey in colour, and contain a great abundance of quartz and of muscovite mica. The lithological nature of this fine sediment is so similar throughout that there is little doubt that it has all been derived from one and the same source. This conclusion points to the probability that the sediments were all deposited while the areas of land and sea remained approximately the same, and consequently there is a presumption that all the sediments were deposited during the same geological period.

It may therefore be taken as a fact that palaeontological, stratigraphical, and lithological evidence alike support the belief that the series of rocks exposed on the coast-line between Wanganui and Hawera represents a period of continuous sedimentation which in New Zealand geology may be said to belong to the upper part of that great geological system which we, by somewhat extending the classification of Captain Hutton, have called the Oamaru system. We are of opinion that the Wanganui system must now be regarded as having lost its individuality, and that it must in future be looked upon as the upper strata of the great Oamaru system. We consider it possible that the period of deposition of these rocks extended

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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: If 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 during the late Tertiary in this country. At least three genera which indicate warm conditions—Melina, 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 conclusion 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: We 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, however, 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.

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It has frequently been remarked before by one of us when speaking of the molluscan fauna of the earlier portion of the Oamaru system—notably that of Target Gully—that it was distinctly richer than that of the present day. It is hardly correct to make this statement in speaking of any comparison between the fauna of the Waipipi series and that of the Castlecliff series. The fauna that has been collected from the former locality up to the present time is not very extensive, and it is notably wanting in the smaller species. These facts effectively prevent a complete comparison being made. It can, however, be safely said that, while the Castlecliff fauna contains a large number of species that are not found at Waipipi, most of these additional species have been found elsewhere in Tertiary rocks of greater age than those of the Waipipi series.

During the time that elapsed between the Waipipi and the Castlecliff periods of deposition, perhaps Upper Miocene to Upper Pliocene, a period elsewhere estimated as equal to a lapse of 690,000 years, an important change took place in the fauna. This change was not the result of the introduction or addition of new species or of new genera, but was due to the extinction of some genera which had been of importance up to the middle of the period, and of numerous species that had given a definite character to the earlier fauna.

As has already been remarked, the molluscan fauna of the Castlecliff series differs in few respects from the Recent fauna. It is probable that the difference is even less than a comparison of the lists would suggest, for the Castlecliff beds were deposited at a depth that approached 100 fathoms, and we have at present an incomplete knowledge of the fauna of the New Zealand sea-floor at that depth. Dredgings that were made outside the Great Barrier in 1904 brought to light several species that had previously been collected in the Castlecliff series, and had been thought to be extinct. From our work on the mollusca of the beds on the Wanganui coast-line we consider that we have a knowledge of at least the main features of the New Zealand marine mollusca from the Upper Miocene to the present day. Such a knowledge must shed an important light on theories that have been advanced in regard to the relations or land connections between New Zealand and other countries during this lapse of time. A number of eminent authorities have written on this subject, but at the present moment we wish to restrict ourselves to those who have made specific statements in regard to these land connections during the period with which we have dealt—namely, from the Upper Miocene to the present day. Hutton* has definitely stated that during the older Pliocene New Zealand was in direct communication with New Gumea. The statement is based mainly on the occurrence of Diflodon aucklandicus in lignite-beds at the Dunstan, in Otago, a species which is said by Hutton to have its nearest ally in New Guinea. We consider it to be impossible that a continental extension of such a magnitude should have occurred without having the greatest effect on the molluscan fauna of New Zealand at that time, and of this we have not been able to find any trace. Marshall has stated that the great Pleistocene elevation connected New Zealand with some of the northern tropical islands, and provided also a shallow-water connection with Antarctica. This statement was based on older opinions of Hutton. It is sufficient

[Footnote] * F. W. Hutton, Index Faunae Novae Zealandiae, p. 18, Dulau and Co., 1904.

[Footnote] † P. Marshall, New Zealand and Adjacent Islands, p. 49, Carl Winter, Heidelberg, 1912.

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to say that a comparison of the mollusca of the Castlecliff beds with the Recent mollusca shows definitely that New Zealand did not at that time receive additions of any importance whatever to its marine molluscan fauna, and therefore that any extension of the area of New Zealand at that time did not in any way impair its isolation.

Park* has stated that during the Pleistocene the area of New Zealand was many times greater than now, that the whole of the South Island and most of the North Island was glaciated, and in a map he shows the land extending to New Caledonia The general similarity between the fauna of the Castlecliff beds and the Recent fauna goes far to disprove the idea of glaciation of this district, while there is no evidence known to us, so far as the mollusca are concerned, that would show a Pleistocene extension of New Zealand to New Caledonia. Hutton in various other publications urged not only that New Zealand was greatly extended during the early Pliocene, but also that it was heavily glaciated at that time. It is probable that in the rock-series that we have described the Nukumaru series is about the age of the early Pliocene. In these beds we have at once a proof that this part of New Zealand was not elevated at that time, and we also have distinct proof that the climate was no colder, but was probably a good deal warmer than at the present day.

There are, however, clear proofs that New Zealand, or at least this part of the country, was considerably elevated at the close of the time of deposition of the Castlecliff beds. Two of these may be quoted. Artesian wells in the lower valley of the Wanganui River bed have reached a depth of 400 ft. without passing through the alluvial matter that the river has deposited. The valley of the Waingongoro River had a bed that extended to an unknown depth below the present sea-level, and had a width of about half a mile at the present beach-level. In addition to these facts, the strata of the series of rocks that has been described have all been elevated and eroded off to a uniform level before the next series of rocks was deposited. This upper rock-series rests in all cases unconformably on those that we have described, lying directly on the Whakino-Waihi beds in the extreme north of the district at which we have worked. The general occurrence of the sediments suggests that all the overlying beds were removed by erosion before these Pleistocene sediments were deposited. As to the precise age of this upper series of rocks we have at present no exact information. They frequently contain a large number of molluscan fossils at the base, but we have seen no extinct species of mollusca among them, and it is probable that they are approximately equivalent to the Pleistocene of Europe. Thomson has lately proposed to apply the name “Hawera series” to them. There is no particular objection to this, though the term “Pleistocene” has long been used in New Zealand, and it has not yet been shown that they are not a reasonable equivalent of the European Pleistocene.

It is perhaps advisable to recapitulate that after the Castlecliff series had been deposited there was a prolonged period of moderate elevation during which a great deal of erosion took place. Though this elevation was considerable, it was not great enough to bring the New Zealand area sufficiently close to any other country to allow of the introduction of any new features into the marine molluscan fauna of New Zealand.

The work that has been done in recent years on the fossil and Recent mollusca of New Zealand is now of sufficient amount and importance

[Footnote] * J. Park, Geology of New Zealand, p. 14, 1910.

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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, 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 Zealandiae, 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 currents and other favourable conditions they are able to travel long distances. The southern portion of Australia, or at least Tasmania, may be said to lie in the region of the “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

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

[Footnote] † Ibid., p. ii.

[Footnote] ‡ F. W. Hutton, Index Faunae Novae Zealandiae, Introduction, pp. 13–19, 1904.

[Footnote] § H. Suter, Manual of the New Zealand Mollusca, pp. v, vi, 1913.

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the result of a colonization across shallow water, or from a land close at hand, we should have expected to find a compact assembly, and not the more or less scattered fragments that are actually found.

Apart from the Australian element, the marine mollusca possess no characters suggestive of recent accessions from other faunal regions, for the Antarctic element is very largely a relic from older geological times.

The terrestrial and fresh-water mollusca require for their dispersal a close approach of lands, if not an actual land bridge. It is true that occasionally marine currents may bring some species to oceanic islands, but if these were introduced in some far-off period it would be extremely difficult, if not impossible, to be certain as to their origin.

Of the land mollusca which have been grouped under the Flammulinidae, Endodonta and Laoma comprise by far the greater number of our snails. They are ancient inhabitants and a primitive race. The geographic range of the group is almost world-wide, but palaeontology so far has found very little record of them. Pilsbry* remarks that “the Carboniferous of Nova Scotia has afforded a small helicoid which in form and sculpture can only be compared with such Endodontidae as Pyramidula or Charopa.” In support of our belief in the great antiquity of these helicoids, it may be pointed out that a number of genera appear to have developed in our area and are restricted to it, and that no New Zealand species has been recorded from any other faunal region. Of other groups, the Athoracophoridae may perhaps have been developed in our region. The Rhytidae, which include our large carnivorous snails, are of very ancient lineage. The operculate group is in great measure peculiar to our fauna. Hedley remarks on this when he discussed the relation of the fauna and flora of Australia to that of New Zealand. Partly to account for the dispersal of Placostylus Hedley constructed his Melanesian Plateau. If that land area or archipelago be granted a great antiquity it would appear to provide all the necessary communications even for the most primitive forms.

The groups of fresh-water mollusca are in perfect accord with the land mollusca. Gundlackia, Potamopyrgus, Lymnaea, Isidora, and Melanopsis are all of ancient lineage, while Diplodon is recorded from our Cretaceous beds at the Malvern Hills. Hedley,§ writing on the surviving refugees of ancient Antarctic life, discusses many interesting problems of distribution. He regards their advent as taking place by circuitous routes at wide intervals of time, and thinks that they are of great antiquity.

In our younger rocks the percentage of Recent species is very high, and in making comparisons between these we prefer to use the names of definite horizons where the species have actually been collected, rather than period-names, which may often involve incorrect correlation.

For the first of these we select the blue clays and sands of the coastal cliffs near Castlecliff. The fauna of these beds differs from the Recent fauna only in the presence of Ataxocerithium, and in the absence of a few obscure genera and a few groups whose habitat is between tide-level or in very shallow water. The total of extinct species is here not more than 7 per cent.

In the Kai Iwi beds, three-quarters of a mile south of the stream, the fauna presents no distinctive features from that at Castlecliff, except

[Footnote] * Manual of Conchology, vol. 9, p xxxix, 1894.

[Footnote] † Natural Science, vol. 3, p. 189, 1893.

[Footnote] ‡ Proc. Linn. Soc. N.S.W., vol. 7, ser. 2, pp. 337–39, 1893.

[Footnote] § Proc. Roy. Soc. N.S.W., vol. 29, pp 278–86, 1895.

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perhaps a slightly higher percentage of extinct forms. Nukumaru beach, from the boat-landing to a point one mile to the south of it, has a fauna that shows a somewhat marked difference, not only in the greater percentage of extinct forms and in the occurrence of the genera Melina and Lutraria, but the assembly of species has changed notably. Some of the Recent species are in great abundance, others have distinctly decreased, and others are uniformly distributed; and in addition to this several are characterized by their unusually large size.

The Waipipi beds, from a quarter of a mile south of the stream to three miles to the north of it, show a still more marked change of fauna. In addition to the genera Melina and Lutraria, there are Crassatellites, Miltha, Cardium and Olivella, a difference in the assembly of Volutes, Dentalium, Pecten, and Struthiolaria. The abundance of the individuals of extinct species is somewhat pronounced as compared with the Recent, and the large species are in particular abundance.

The Whakino-Waihi beds, on the coast near Hawera, have a fauna closely similar to that of the Waipipi beds. The percentage of extinct species is only slightly greater, but there is a difference in the prominent species. Lutraria has not been found; Melina, Cardium, and Crassatellites are scarce, while Pecten, Natica and Dentalium, are in great abundance; Chione chiloensis is not uncommon. Of the Recent species, Atrina zelandica and Ostrea angasi are in great abundance.

It has already been pointed out that from Castlecliff to Waipipi there is an unbroken stratified series. We now extend that series to Waihi, and note that within its limits we see a most marked faunal change within a continuous series of deposits. Had it so happened that the beds that lie between the different horizons that are mentioned above had not been preserved, and that the several fragments had been so disturbed that stratigraphical evidence was practically valueless, palaeontology would then have been the only guide to their respective ages. It would have been evident that Castlecliff and Kai Iwi were essentially of the same age. The Nukumaru beds, on the other hand, might well have been regarded as a formation of a different period, and in the Waipipi strata the faunal change is so great that they would probably have been assigned a greater antiquity than they actually possess. On the other hand, the Whakino-Waihi beds are so similar in fauna to those at Waipipi that they would probably have been placed in the same horizon, whereas they are actually separated by several hundred feet of strata. The change in the fauna was slow between the Waihi-Whakino and Waipipi stages, and between the Kai Iwi and Castlecliff stages, but it was relatively rapid between the Waipipi and Nukumaru stages. This rapidity, we think, marks a great change in the physical or climatic conditions of the time.

It may fairly be claimed that there were no important accessions to the fauna during the Castlecliff to Whakino-Waihi period of deposition, for, as stated previously, the majority of the Recent genera are represented, and usually by Recent species, and the extinct species that occur in any abundance have already been recognized in earlier formations in New Zealand. Even genera such as Couthouyia, Ataxocerithium, and Melina occur at Target Gully, and a fragment of Miltha, perhaps similar to the Waipipi species, has been collected at Mount Donald.

While the Waihi beds are the lowest of the unbroken series of deposits on this coast, and while the palaeontology of the Tawhiti beds as recorded by Marshall, and the Ormond beds as recorded by Henderson and Ongley, indicate a fairly close relationship, we cannot claim that the one would

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directly succeed the other. It is, however, perfectly clear that there is a far closer relationship between the Waihi and Tawhiti beds than between the Waihi and Castlecliff beds. The change from the Tawhiti to the Waihi beds does not in any way suggest that elements of a new fauna were introduced between these periods. On the other hand, the Tawhiti fauna is as closely related to the fauna of Target Gully as it is to the Waihi fauna. And, again, there is no indication of the introduction of new elements to the marine molluscan fauna during that interval of time.

The various lists that have now been published of the mollusca of many Tertiary horizons near Oamaru enable us to carry this review a little further. These lists appear to indicate a gradually changing fauna; nowhere does there seem to be an inrush of additional types. The genera that we have in our marine mollusca now were practically all present at the time that the Target Gully beds were deposited. The fauna of that time was certainly richer than the present one. The change that has taken place since then has been of the nature of reduction rather than of addition. We have, then, been forced to the conclusion that from the time the Wangaloa and Hampden beds were deposited until the present day the marine mollusca of New Zealand has shown a gradual development without any important additions at any time from other fauna regions. This, of course, implies that New Zealand has been completely isolated throughout this long interval of time.

The genera Murex and Trophon, that Hutton* refers to as having reached New Zealand from the Australian region in Pliocene time, have now been collected from Target Gully. The statement of Hutton that Typhis is of Eocene occurrence in Australia and Miocene in New Zealand needs revision, for the Australian Eocene is now generally classed as Miocene, while Typhis occurs as low as the Wharekuri beds in New Zealand. Further and more careful comparison of Australian and New Zealand specimens of Pectunculus laticostatus is necessary before any conclusions can be drawn from the time of appearance of the species in the Tertiary rocks of these countries. Dosinia greyi has been recorded from Wangaloa by Marshall. It is thus clear that the palaeontological proofs brought forward by Hutton in 1904 of a Tertiary land connection with Australia fall to the ground in the light of the fuller information that has since been acquired.

It has been frequently suggested that the resemblance between the Miocene fossils of South America and those of New Zealand is so great that it proves that those lands were either actually connected in the middle Tertiary or were separated by a narrow stretch of water only. Accurate comparisons have shown that many of these identifications were inaccurate, and the number of species common to the two lands has now been reduced by Suter to six only. It is probable, however, that still further comparisons are required. It is, at any rate, noticeable that the six species referred to do not occur in the same Tertiary horizon in New Zealand, and that half of them occur in our lowest Tertiaries (Wangaloa and Hampden), which are probably equivalent to the Eocene of Europe. Recent work has shown that it is very noticeable that the Cretaceous fossils of Seymour Island are far more similar to the Cretaceous of New Zealand than the Tertiary fossils of the same locality are to those of this country. The Navidad and South Patagonian Tertiary fossils also are distinctly different from those of New Zealand.

[Footnote] * F. W. Hutton, Index Faunae Novae Zealandiae, Introduction, p. 18, 1904.

[Footnote] † C. Chilton, Subantarctic Islands of New Zealand, vol. 2, p. 805, Government Printer, Wellington, 1909.