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Volume 47, 1914
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Art. XL.—Cainozoic Fossils from Oamaru.

[Read before the Otago Institute, 1st December, 1914.]

Further collecting in the fossiliferous beds of Tertiary age near Oamaru has been continued on many occasions by Mr. Uttley and myself with several assistants. It has been thought worth while to put on record the names of those fossils that we have found, and to add to these lists stratigraphical and lithological notes of an explanatory nature. For the statements that are made here the author alone is responsible, but he is indebted to Mr. Uttley for much information.

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Fig. 1.–Sketch-map of Oamaru district, showing localities where fossils were collected.

The accompanying map shows the locality of the various places where we have made collections, and it will be seen generally that collections have been obtained from various points from All Day Bay, on the coast, ten miles south of Oamaru, to Wharekuri, in the Waitaki Valley, forty miles distant from the sea, and in the Waihao Valley, twenty miles to the north of Oamaru.

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In the lists given here Mollusca only are classified. The Brachiopods of New Zealand are being separately reclassified by Dr. J. A. Thomson. The teeth of sharks are relatively few in this formation, and the Corals, Foraminifera and Polyzoa have not been separately collected. It is not supposed that the collections are exhaustive, though it is probable that relatively few species will hereafter be added to the list from Target Gully. The work of identification would have been impossible without the kind and generous assistance of Mr. H. Suter, who has also named a large number of the new species, and his descriptions of these will shortly be published in Bulletin No. 3 of the Palaeontological series of the New Zealand Geological Survey.

Target Gully.

Some three days have been spent at Target Gully, Oamaru, in adding to the collections previously made there. The following is a complete list, including the species that have been named by Suter. The description of these will be given in Bulletin No. 3 of the Palaeontological series of the New Zealand Geological Survey.

  • Schismope atkinsoni T.-Woods.

  • Emarginula striatula Q. & G.

  • Trochus tiaratus Q. & G.

  • Monilea simplex Suter.

  • Lissospira exigua Suter.

  • Circulus politus Suter.

  • Leptothyra fluctuata Hutton.

  • Cerithiopsis aequicincta Suter.

  • Newtoniella fidicula Suter.

  • Serpulorbis sp.

  • Turritella carlottae Watson.

  • concava Hutton.

  • rosea Q. & G.

  • murrayana Tate.

  • patagonica Sowerby.

  • Eglisia striolata Hutton.

  • Struthiolaria tuberculata Hutton.

  • cincta Hutton.

  • Calyptraea maculata Q. & G.

  • alta Hutton

  • maccoyi Suter.

  • Crepidula crepidula L.

  • densistriata Suter.

  • striata Hutton.

  • costata Sowerby.

  • incurva Zittel.

  • Natica zelandica Q. & G.

  • Polinices suturalis Hutton.

  • gibbosus Hutton

  • cinctus Hutton.

  • Cymatium minimum Hutton.

  • — sp.

  • Epitonium browni Zittel.

  • rugulosum lyratum Zittel.

  • Turbonilla zelandica Hutton.

  • oamarutica Suter.

  • Odostomia pudica Suter.

  • rugata Hutton.

  • Fusinus sp.

  • Latirus brevirostris Hutton.

  • elatior Suter.

  • compactus Suter.

  • acuticingulatus Suter.

  • — n. sp.

  • Mitra enysi Hutton.

  • Vexillum rutilidomum Hutton.

  • Siphonalia dilatata Q. & G.

  • costata Hutton.

  • conoidea Hutton.

  • turrita Suter.

  • excelsa Suter.

  • Euthria striophora Suter.

  • Cominella pulchra Suter.

  • huttoni Kobelt.

  • intermedia Suter.

  • Alectrion socialis Hutton.

  • tatei T.-Woods.

  • Murex octogonus Q. & G.

  • angasi Crosse.

  • Trophon lepidus Suter.

  • paivae Crosse.

  • Typhis maccoyi T.-Woods.

  • Admete praecursoria Suter.

  • Fulguraria arabica Martyn.

  • elongata Swainson.

  • gracilis Swainson.

  • — n. sp.

  • Lapparia corrugata Hutton.

  • Ancilla australis Sowerby.

  • pseudaustralis Tate.

  • bicolor Gray.

  • hebera Hutton.

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  • Marginella harrisi Cossman

  • conica Harris.

  • Erato striata Suter.

  • Drillia imperfecta Suter.

  • callimorpha Suter.

  • Surcula fusiformis Hutton.

  • awamoaensis Hutton.

  • Bathytoma sulcata Hutton.

  • anticostata Suter.

  • perlata Suter.

  • Turris altus Harris.

  • —— transennus Suter.

  • Mangilia brachyspira Suter.

  • infelix Suter.

  • canaliculatus Suter.

  • tenuilirata Suter.

  • leptosoma Suter.

  • rudis Hutton.

  • sinclairi Smith.

  • Terebra orycta Suter.

  • costata Hutton.

  • Ringicula uniplicata Hutton.

  • Cylichnella enysi Hutton.

  • striata Hutton.

  • soror Suter.

  • Volvulella reflexa Hutton.

  • Hemiconus trailli Hutton.

  • Dentalium solidum Hutton.

  • mantetti Hutton.

  • nanum Hutton.

  • Nucula hartvigiana Phil.

  • Malletia australis Q. & G.

  • Anomia huttoni Suter.

  • Placunanomia incisura Hutton.

  • zelandica Gray.

  • Arca decussata Gray.

  • australis Hutton.

  • subvelata Suter.

  • Glycymeris laticostata Q. & G.

  • globosa Hutton.

  • Cucullaea alta Sowerby.

  • Limopsis zitteli Ihering.

  • catenata Suter.

  • Pecten radius Hutton.

  • burnetti Hutton.

  • huttoni Park.

  • Lima colorata Hutton.

  • bullata Born.

  • Mytilus striatus Hutton.

  • Ostraea angasi Hutton.

  • nelsoniana Zittel.

  • Crassatellites obesus A. Adams.

  • attenuatus Hutton.

  • amplus Zittel.

  • Venericardia difficilis Deshaves.

  • pseutes Suter.

  • Diplodonta globularis Lamarck.

  • Loripes laminata Hutton.

  • Divaricella cumingi Adams and Angas.

  • Tellina glabrella Deshayes.

  • Zenatia acinaces Q. & G.

  • Dosinia magna Hutton.

  • greyi Zittel.

  • Macrocallista multistriata Sowerby.

  • Chione meridionalis Sowerby.

  • mesodesma Q. & G.

  • yatei Gray.

  • Paphicurta Hutton.

  • — n. sp.

  • Cytherea oblonga Hanley.

  • sulcata Hutton.

  • subsulcata Suter.

  • Cardium patulum Hutton.

  • — n. sp.

  • Psammobia lineolata Gray.

  • Corbula pumila Hutton.

  • canaliculata Hutton.

  • humerosa Hutton.

  • caiparaensis Suter.

  • Panopaea sp.

  • Myodora subrostata E. A. Smith.

  • Chamostraea albida Lamarck.

  • Chama huttoni Hector.

  • Teredo heaphyi Zittel.

Additional species since obtained are—

  • Hinnites trailli Hutton.

  • Protocardia sera Hutton.

  • Trivia n. sp.

  • Mitra n. sp.

The total number of species in this list is 155, of which forty-seven species are Recent—a percentage of 33. The collections that we have made at Target Gully illustrate forcibly the errors that are likely to arise if, for the purpose of classifying strata, importance is laid on the absence of species or genera of fossils found in incomplete collections which may be used to

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arrange the Cainozoic formations of New Zealand in a chronological sequence. Thus the first year's collecting in these beds gave us no Epitonium, Cardium, Paphia, Fusinus, or Mangilia; while Murex, Latirius, and Struthiolaria were poorly represented.

The present list appears to be sufficiently complete to establish a definite horizon, which stratigraphically lies almost directly on the Hutchinson's Quarry beds, which in its turn admittedly rests on the Oamaru limestone. The fauna appears to be characteristic of a depth of about 40 fathoms. The incomplete filling of many of the larger shells with sediment, and the uninjured nature of such shells as Murex, show that the sea-floor was not subject to much disturbance. The fact that many shells are broken must probably be ascribed to fish. The grains of glauconite, which are quite frequent, point to slow accumulation and an extensive shore-line situated many miles away.

The number of species of Mollusca collected in this small shell-bed, 4ft. high and 6 ft. long, is more than one-seventh part of the number of the Recent species of New Zealand Mollusca recorded in Cheeseman's Manual.

Wharekuri.

The locality from which we have collected at Wharekuri is on the bed of the Waitaki River, about forty miles from the sea The actual spot is about one mile below Wharekuri, and on the opposite (or left) bank of the river. Lithologically the beds consist of a marly greensand, and dip about 2° to the north. There can be no doubt that they directly overlie the Kekenodon beds of McKay, classed by him with the Upper Eocene.* They are, in fact, identical with the fossiliferous horizon on the opposite bank of the river, referred to by McKay.

Hamilton subsequently showed that in the extreme southern portion of this Tertiary basin the rocks are cut by several fault-planes. From the Kekenodon beds of McKay Hamilton obtained a good specimen of Aturia ziczac var. australis.

Park classed these strata as the equivalent of the Mount Brown beds, the middle member of his Miocene system. The whole series of Cainozoic beds is certainly conformable, as shown by Park, though the large fault inserted by him is unnecessary.

In the Wharekuri basin the lowest rocks of the Tertiary sequence are quartz gravels, a fact that has considerable significance. The quartz is undoubtedly derived from schist, and the area of schist rocks is now separated from the Waitaki Valley by Mount Domett and the Kakanui Ranges, with an average elevation of about 4,000 ft.

The occurrence of the quartz gravels, therefore, practically proves that the range of the Kakanui Mountains did not then exist, for in such a narrow fiord as the present Waitaki Valley would have been if the Kakanui Range had then existed the floor must have been covered with detritus derived from the slopes of the neighbouring range—that is, with material derived from the waste of greywacke rocks—a deposit that is quite common in New Zealand, and quite different from the nearly pure quartz gravels of which the lowest Tertiary rocks are composed.

[Footnote] * Rep. Geol. Surv., 1881, p. 67.

[Footnote] † Trans. N.Z. Inst., vol. 36, 1904, p. 465.

[Footnote] ‡ Trans. N.Z. Inst., vol. 37, 1905, p. 525.

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In the floor of the Awahokomo Valley, about three miles from the point where it joins the Waitaki, the junction of the Tertiary strata with the Maitai rocks of which the Kakanui Mountains are formed is to be clearly seen. The actual plane of junction dips 73° to the south, and strikes 15° west of north. The Maitai rocks to the south of the plane of junction are greatly shattered. This is best seen when the line is followed over the hills which lie to the north of the Awahokomo. The weathering of the rocks has here developed their shattered nature, and they break down into a clayey material, which still contains angular fragments of rock. This shattered material has been called by McKay “glacier deposits.”*

There can be no doubt that this plane of junction is a thrust-plane, though more highly inclined than is usual for such planes. This high inclination of a thrust-plane appears to be a feature of those examples that have been described in New Zealand.

In the present case the great tectonic movement has had relatively little effect on the Cainozoic sediments over which the Maitai rocks have been thrust. These are in no way crushed, and the fossils which are contained in them are not distorted. This again appears to be a feature of New Zealand Tertiaries when they are involved in tectonic movements. The fossils in the narrow band of Tertiary rocks, only 15 ft. wide, at Stony Creek, near Lake Wakatipu, with schist on both sides of it, are not distorted, and again the rock is not crushed. In the Clarence Valley the rocks are not fossiliferous, but their structure does not appear to have suffered in any way by the great tectonic movements which have been so well described by Cotton.

On the northern bank of the river the beds soon rise gradually, and before long the basal quartz gravels with coal-seams are exposed. They contain good specimens of fossil wood similar to that described by Unger as Nicolia.

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Fig. 2.—Section across Wharekuri Basin.

Away from the river the ground rises somewhat more steeply, and highly siliceous greensands are seen to rest on the quartz gravels. These greensands contain Cucullaea, Venericardia, Dentalium, and Natica rather badly preserved, but apparently similar to the species that were found in the river-bank. In the Awahokomo Valley the same genera were found in a greensand lying only 20 ft. above the quartz gravels, which there contain coal-seams. There is obviously every reason to believe that the whole of the younger rocks in the Wharekuri Basin belong to the same series.

On the north-east side of this basin of Tertiary rocks the Maitai sediments rise abruptly in a steep scarp for about 1,000 ft., and this scarp is but little incised by the erosion of the streams that flow down it. The outcrop is separated from that of the Tertiary rocks by a distance of about 30 ft. only,

[Footnote] * Rep. N.Z. Geol. Surv., 1881, p. 60.

[Footnote] † Cotton, Geogr. Mag., 1913, p. 227.

[Footnote] ‡ “Reise der ‘Novara,’ ” 1865 Geologischer Theil, Band 1 p. 13.

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and the two series appear to be separated from one another by a normal fault. The diagram, fig. 2, therefore represents the author's opinion of the structure of this interesting basin of Tertiary rocks.

The following is a list of the fossils found in the marly greensands on the left bank of the river about a mile below Wharekuri, which were obtained as a result of two days' collecting:—

  • Turritella ambulacrum Sowerby.

  • pagoda Reeve.

  • symmetrica Hutton.

  • carlottae Watson.

  • Struthiolaria cincta Hutton.

  • Calyptraea maculata Q. & G.

  • Polinices gibbosus Hutton.

  • huttoni Ihering

  • cinctus Hutton.

  • ——suturalis Hutton.

  • Cymatium minimum Hutton.

  • Epitonium rugulosum lyratum Zittel.

  • — n. sp.

  • Niso n. sp.

  • Fusinus sp.

  • Siphonalia nodosa Martyn.

  • excelsa Suter.

  • Cominella exsculpta Suter.

  • pulchra Suter.

  • Alectrion socialis Hutt.

  • Lapparia corrugata, Hutton.

  • Fulguraria gracilis Swainson.

  • Ancilla pseudaustralis Tate.

  • bicolorata Hutton.

  • Marginella harrisi Cossman.

  • Turris uttleyi Suter.

  • Drillia callimorpha Suter.

  • Surcula fusiformis Hutton.

  • hamiltoni Hutton.

  • Bathytoma sulcata excavata Suter.

  • Mangilia cincta Hutton.

  • rudis Hutton.

  • Exilia dalli Suter.

  • Cylichnella enysi Hutton.

  • Xenophora sp.

  • Dentalium mantelli Zittel.

  • solidum Hutton.

  • Leda semiteres Hutton.

  • bellula A. Adams.

  • Malletia australis Q. & G.

  • Anomia trigonopsis Hutton.

  • walteri Hutton

  • Glycymeris cordata Hutton.

  • Cucullaea attenuata, Hutton.

  • Limopsis aurita Brocchi.

  • zitteli Ihering.

  • Pecten chathamensis Hutton.

  • hutioni Park.

  • Ostraea tatei Suter.

  • Crassatellites obesus A. Adams.

  • Venericardia pseutes Suter.

  • Loripes laminata Hutton.

  • Dosima greyi Zittel

  • Macrocallista multistriata Sowerby.

  • Chione meridionalis Sowerby.

  • Cardium patulum Hutton.

  • Psammobia lineolata Gray.

  • Corbula humerosa Hutton.

  • canaliculata Hutton.

  • Teredo heaphyi Zittel.

Fourteen species in this list of sixty are Recent, a percentage of 23.3. The most abundant of these fossils are Polinices huttoni, Cucullaea attenuata, Venericardia pseutes, Crassatellites obesus, and amongst the smaller shells Limopsis zitteli.

The only other list of species of Mollusca from this locality is that given by Park.* Park's collection, however, was made on the other side of the river. It contains thirty-nine species, of which only twelve are identical with the species listed here.

Otiake.

There is a prominent exposure of limestone on the right bank of the Waitaki, about five miles below Kurow. It lies half a mile distant from the railway-line between Oamaru and Kurow, on its southern side, just below

[Footnote] * Trans. N.Z. Inst., vol. 37, 1905, p. 525.

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the bridge over the Otiake Stream. The limestone is of an arenaceous nature, and contains a great number of fossils. Near its base there is a thin band of greensand, which contains many specimens of Isis dactyla, Magellania sp., and Pecten huttoni.

The following is a list of the species obtained during two days' collecting from a face of arenaceous limestone some 50 ft. in height:—

  • Turritella cavershamensis Harris.

  • murrayana Tate.

  • Struthiolaria vermis Martyn.

  • Crepidula gregaria Sowerby.

  • striata Hutton.

  • Calyptraea maculata Q. & G.

  • Natica zelandica Q. & G.

  • Polinices huttoni Ihering.

  • suturalis Hutton.

  • cinctus Hutton.

  • gibbosus Hutton.

  • Trichotropis clathrata Sowerby.

  • Epitonium rugulosum lyratum Zittel.

  • Fusinus sp.

  • Mitra n. sp.

  • Siphonalia conoidea Zittel.

  • nodosa Martyn.

  • Cominella pulchra Suter.

  • Murex zelandicus Q. & G.

  • Typhis maccoyi T.-Woods.

  • Fulguraria gracilis Swainson.

  • Lapparia corrugata Hutton.

  • Ancilla hebera Hutton.

  • bicolorata Gray.

  • mucronata Sowerby.

  • Marginella harrisi Cossman.

  • Turris altus Harris.

  • altus transennus Suter.

  • uttleyi Suter.

  • Exilia dalli Suter.

  • — n. sp.

  • Terebra orycta Suter.

  • Surcula n. sp.

  • — n. sp.

  • Drillia callimorpha Suter.

  • Bathytoma sulcata excavata Suter.

  • Euthria sp.

  • Mangilia rudis Hutton.

  • tenuilirata Suter.

  • — n. sp.

  • Dentalium solidum Hutton.

  • mantelli Zittel.

  • Cucullaea attenuata Hutton.

  • Limopsis aurita Brocchi.

  • Modiolus australis Gray.

  • Pecten zelandiae Gray.

  • huttoni Park.

  • Lima colorata Hutton.

  • Crassatellitus obesus A. Adams.

  • Venericardia difficilis Deshayes.

  • Divaricella cumingi Adams and Angas.

  • Zenatia acinaces Q. & G.

  • Dosinia greyi Zittel.

  • Cytherea oblonga Hanley.

  • — n. sp.

  • Macrocallista multistriata Sowerby.

  • assimilis Hutton.

  • Corbula canaliculata Hutton.

  • humerosa Hutton.

  • caiparaensis Suter.

  • Teredo heaphyi Zittel.

This list contains sixty-one species, of which fifteen are Recent, a percentage of 24. No collecting has previously been done in this locality.

All Day Bay.

In this locality the lowest rock is a volcanic breccia commonly known in New Zealand geology as the Waireka tuffs. A bed of limestone about 12 ft. thick rests on the breccia quite conformably. The upper surface of the limestone is remarkable for the abundant remains of species of Isis. This upper surface is somewhat uneven, as is generally the case in New Zealand when the limestone is succeeded by a bed of greensand, which is the case here. The greensands gradually become argillaceous, and within a thickness of 50 ft. they pass into a material that cannot be distinguished from the Awamoa beds, which five miles farther north are clearly seen at the Rifle Butts to have exactly the same stratigraphical position. No lists of fossils from this locality have been published previously. The

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following twenty-seven species were found by us in the course of one day's collecting:—

  • Turritella cavershamensis Harris.

  • Polinices gibbosus Hutton.

  • Cymatium n. sp.

  • Phalium achatinum pyrum Lamarck.

  • Epitonium browni Zittel.

  • Turbonilla oamarutica Suter.

  • Mitra n. sp.

  • Vexillum apicale Hutton.

  • Typhis maccoyi Tate.

  • Murex octogonus Q. & G.

  • Lapparia corrugata Hutton.

  • Ancilla bicolorata Gray.

  • — n. sp.

  • Marginella conica Harris.

  • Marginella harrisi Cossman.

  • Turris altus Harris.

  • Mangilia rudis Hutton.

  • Dentalium mantelli Hutton.

  • Placunanomia zelandica Gray.

  • Limopsis zitelli Ihering.

  • Nucula hartvigiana Phil.

  • Pecten huttoni Park.

  • Lima colorata Hutton.

  • Crassatellites obesus A. Adams.

  • Venericardia australis Lamarck.

  • Macrocallista assimilis Hutton.

  • Corbula pumila Hutton.

Only six of these twenty-seven species are known to be Recent, a percentage of 22.2. As stated previously, the beds at All Day Bay are similar stratigraphically and lithologically to the Awamoa beds, but in a collection of sixty-four species made at Awamoa in 1912 the percentage of Recent species was found to be as high as 35.5.

Rifle Butts.

At this locality, which is situated a short distance to the south of Cape Wanbrow, the strata are dipping to the south at an angle of 35°. The sequence is here perfectly plain, and the highest beds are composed of bluish clay similar to that at Awamoa and All Day Bay. In descending order, these are succeeded by greensands, limestone, and tuffs. Here, as at many other places near Oamaru, the continuous deposition has been greatly interrupted by the volcanic eruptions of the vicinity, which have caused beds of tuff to be associated with the blue clay. Collections of Mollusca were made from the blue clay, with the following result:—

  • Tuiritella patagonica Sowerby.

  • concava Hutton.

  • sturtii Tate.

  • — n. sp.

  • Crepidula gregaria Sowerby.

  • Natica zelandica Q. & G.

  • Polinices suturalis Hutton.

  • gibbosus Hutton.

  • amphialus Watson.

  • Turbonilla oamarutica Suter.

  • Phalium achatinum pyrum Lamarck.

  • Vexillum apicale Hutton.

  • linctum Hutton.

  • Siphonalia turrita Suter.

  • Alectrion socialis Hutton.

  • Ancilla bicolor Gray.

  • Marginella pygmaea Hutton.

  • conica Harris.

  • Marginella harrisi Cossman.

  • Turris altus Harris.

  • Drillia awamoaensis Hutton.

  • Surcula fusiformis Hutton.

  • — n. sp.

  • Bathytoma albula Hutton.

  • Mangilia rudis Hutton.

  • protensa Hutton.

  • leptosoma Hutton.

  • Cylichnella thetidis Hedley.

  • Dentalium solidum Hutton.

  • Placunanomia zelandica Gray.

  • Cucullaea attenuata Hutton.

  • Pecten scandulus Hutton.

  • Venericardia difficilis Deshayes

  • Loripes laminata Hutton.

  • Tellina glabrella Deshayes.

  • Zenatia acinaces Q. & G.

  • Cytherea oblonga Hanley.

  • Corbula canaliculata Hutton.

Of these thirty-eight species, only ten are Recent—that is, a percentage of 26.3.

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Maerewhenua River.

A small collection was made by Mr. Uttley near the right bank of this river, ten miles distant from the point where it joins the Waitaki. The rock in which the fossils are embedded is a limestone. The following species have been identified:—

  • Turritella carlottae Watson.

  • Capulus australis Lamarck.

  • Polinices amphialus Watson.

  • Sinum n. sp.

  • AnRcilla bicolor Gray.

  • Surcula n. sp.

  • Mangilia n. sp.

  • Cylichnella enysi Hutton.

  • Nucula stangei A. Adams.

  • Venericardia difficilis Deshayes.

  • Cardium waitakiense Suter.

  • — n. sp.

  • Corbula humerosa Hutton.

Waihao Valley.

In this district Mr. Uttley made collections at several different localities, as shown below.

1. Right bank of the Waihao River, three miles below the Waihao Forks, in a bed of greensands which lies conformably below the arenaceous limestone. Ten per cent. of the species are Recent.

  • Turritella concava Hutton.

  • murrayana Tate.

  • carlottae Watson.

  • patagonica Sowerby.

  • Struthiolaria papulosa Martyn.

  • Polinices suturalis Hutton.

  • Galeodea senex Hutton.

  • Alectrion socialis Hutton.

  • Lapparia corrugata Hutton.

  • Ancilla hebera Hutton.

  • Surcula fusiformis Hutton.

  • — n. sp.

  • — n. sp.

  • Bathytoma haasti Hutton.

  • Hemiconus trailli Hutton.

  • Dentalium mantelli Zittel.

  • Limopsis aurita Brocchi.

  • Lima paucisulcata Hutton.

  • Crassatellites obesus A. Adams.

  • Corbula paucisulcata Hutton.

2. Right bank of the Waihao River, at McCulloch's bridge. Here again the fossil-bearing beds consist of greensand which lies conformably beneath the arenaceous limestone. Fifteen per cent. of the species are Recent.

  • Turritella aldingae Tate.

  • ambulacrum Sowerby.

  • Natica zelandica Q. & G

  • Polinices suturalis Hutton.

  • Mitra inconspicua Hutton.

  • Siphonalia turrita Suter.

  • Ancilla bicolor Gray.

  • Turris n. sp.

  • — n. sp.

  • Surcula pareorensis Suter.

  • Mangilia rudis Hutton.

  • Dentalium solidum Hutton.

  • Corbula canaliculata Hutton.

3. Near Mount Harris, on the slope towards the Waitaki Valley—the first outcrop on the road leading from the Waitaki to the Waihao Valley.

  • Turritella murrayana Tate.

  • cavershamensis Harris.

  • concava Hutton.

  • Polinices gibbosus Hutton.

  • Galeodea senex Hutton.

  • Epitonium browni Zittel.

  • Ancilla browni Zittel.

  • bicolor Gray.

  • Drillia n. sp.

  • Surcula fusiformis Hutton.

  • Dentalium mantelli Zittel.

  • Nucula n. sp.

  • Malletia australis Q. & G.

  • Limopsis aurita Brocchi.

  • Crassatellites obesus A. Adams.

  • Venericardia difficilis Deshayes.

  • Zenatia acinaces Q. & G.

  • Cytherea oblonga Hanley.

  • Psammobia lineolata Gray.

  • Corbula caiparaensis Suter.

  • canaliculata Hutton.

  • humerosa Hutton.

– 386 –

The fossils are contained in a stratum of brown sands, which is the material of which Mount Harris is formed. This material overlies the limestone, and is probably a slightly higher horizon than that of the Target Gully beds. Thirty-three per cent. of the species are Recent.

4. The top of the hill from Waihao Forks to the Elephant Hill. The rocks here again are brown sands similar to those of the last locality.

  • Turritella cavershamensis Harris.

  • carlottae Watson.

  • Natica zelandica Q. & G.

  • Polinices suturalis Hutton.

  • — huttoni Ihering.

  • Fusinus n. sp.

  • Siphonalia conoidea Zittel.

  • Alectrion socialis Hutton.

  • Fulguraria arabica Martyn.

  • Ancilla bicolor Gray.

  • Marginella pygmaea Sowerby.

  • Surcula fusiformis Hutton.

  • Surcula n. sp.

  • — n. sp.

  • Bathytoma sulcata excavata Suter.

  • Mangilia, n. sp.

  • Terebra costata Hutton.

  • Cylichnella thetidis Hedley.

  • Thalassohelix igniflua Reeve.

  • Dentalium nanum Hutton.

  • ecostatum T. W. Kirk

  • Crassatellites obesus A. Adams.

  • Venericardia difficilis Deshayes.

  • Corbula canaliculata Hutton.

Of these species, as many as 46 per cent. are Recent.

The general similarity of these lists at once establishes the fact that the rocks in which the fossils occur belong to the same stratigraphical series. This fact is also, in the author's opinion, abundantly proved by the stratigraphical evidence, for no appearance of a stratigraphical break is to be found. Hector and McKay, however, placed these strata in three different formations—Cretaceo-tertiary, Upper Eocene, and Lower Miocene; Hutton placed them partly in the Oligocene and partly in the Miocene; while Park classified them all in the Miocene formation. It is obvious from the foregoing lists that the last opinion is probably correct, though the author differs from Park as to the arrangement of the different beds within this system. The stratigraphical sequence is clearly—

4.

Brown sands.

3.

Grey argillaceous beds (Awamoa).

2.

Limestone.

1.

Greensands.

That this arrangement is supported by the palaeontological evidence is shown by the following considerations: The greensands at Wharekuri contain 23.3 per cent. of Recent species, and those on the Waihao 10 per cent. and 15 per cent. respectively. The lower percentages in the last two cases are based on small and probably quite incomplete collections.

Collections were made from the limestone at Otiake. In this place it has a molluscan fauna which contains 24.2 per cent. of Recent species. Though the limestone has a wide occurrence in the Oamaru district, it seldom contains many molluscan remains, and in most localities the hard and compact nature of the rock makes it almost impossible to extract the shells. In those places only where the limestone is highly arenaceous can the shells be collected with any ease. Park has classified the limestone outcrops at Oamaru in two different series, but we are not able to agree with this from a study of the stratigraphical evidence. The palaeontological evidence as here detailed gives no support to this theory. The fauna of the greensands at Wharekuri and at Waihao appears to be of a distinctly more ancient type than that of the sands which rest on the limestone at Oamaru. Park

– 387 –

would consider these two strata of the same age. The Oamaru limestone generally consists almost entirely of remains of Echinoderms, Polyzoa, and Foraminifera, though the material is generally somewhat fragmentary.

Near the coast at Awamoa, and actually on the coast at the Rifle Butts and at All Day Bay, the rocks which rest on the limestone are a bluish-grey calcareous mudstone. The percentage of Recent species contained in the Mollusca found in these rocks is 35, 26, and 22 respectively. The divergence between these results is considerable, but the collections are of very different values. It is possible that when the collections are more complete the results will be more in accord.

The Target Gully beds are a slightly higher horizon, and the large collection that has been made there contains 33 per cent. of Recent species. The beds of Mount Harris, in rather similar material, give almost the same result; while those of Elephant Hill, which appear to be a still higher horizon, contain as much as 46 per cent. of Recent species.

Thus the relative number of Recent species gradually becomes greater in the higher beds, as would, indeed, be expected; and it is evident that this result, at the least, strongly supports the conclusion as to the relative position of the strata which was dependent upon purely stratigraphical observations.

As to the actual percentages of Recent species, it is probable that considerable changes will be made in the future as the molluscan fauna of the deeper waters off the New Zealand coasts becomes better known. At the present time relatively little dredging has been done, and it cannot be doubted that several species hitherto believed to be extinct will be yet discovered when further work of that nature has been done. It is, however, evident that none of the strata from which the collections described in this paper have been made is older than the Miocene period. This statement, however, involves the question whether any importance is to be attached to the percentage of Recent species. In a country so geographically isolated as New Zealand it is possible that formal change is very slow and that a relatively high percentage of Recent species may be found in strata of relatively high antiquity.