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Volume 53, 1921
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Art. XI.—Fossils from the Paparoa Rapids, on the Wanganui River.

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

No complete collection of fossils has yet been recorded from the strata that crop out along the course of the Wanganui River. For the most part the strata contain but few fossils, and in those localities where organic remains are abundant the material in which they are embedded is pebbly, or it has a concretionary nature, which makes it difficult to extract the fossils in a condition that allows of exact identification. The most promising locality that is known at present is probably that of the Paparoa Rapids, some twenty miles below Taumarunui. Park* was the first geologist to make any collections here, and he recognized some thirty species, the nature of which seemed to show that the strata were of a distinctly lower horizon than any that he found on the coast between Wanganui and Patea. A visit was paid by one of us to the locality in January, 1920, with the object of making as complete a collection as time and circumstances would allow. Two days were spent there, but the collection that was made did not contain a very large number of species. At the Paparoa Rapids the strata on the right bank of the river are almost horizontal, but on the left bank they have been disturbed by an extensive slip, and have locally a high easterly dip. The fossil-bearing rock is a fine, hard, bluish-grey sandstone, slightly concretionary in its nature, and large fossil shells are very conspicuous in it. The actual material of the sands is such as might well be derived from the rocks of Maitai age, of which the main mountain-ranges of the North Island are composed.

The following is a list of the species which were collected, the Recent species being marked with an asterisk.

  • Ancilla sp.; apex only

  • *Calyptraea novae-zelandiae Less.

  • Chione acuminata Hutt.

  • *Chione yatei (Gray)

  • Cominella aff. intermedia Sut.

  • Conus sp.; a fragment only

  • Corbula pumila Hutt.

  • Crassatellites attenuatus (Hutt.)

  • Crassatellites trailli (Hutt.)

  • Crepidula gregaria Sow.

  • Cucullaea worthingtoni Hutt.

  • Cytherea ensyi Hutt.

  • Dentalium solidum Hutt.

  • *Divaricella cumingi (Ad. & Ang.)

  • *Dosinia anus (Phil.)

  • *Dosinia subrosea (Gray)

  • Epitonium lyratum (Zitt.)

  • Glycymeris cordata (Hutt.)

  • Glycymeris subglobosa Sut.

  • Limopsis zitteli Iher.

  • Luponia aff. ovulatella Tate

  • *Mactra scalpellum Reeve

  • Natica (Polinices) gibbosus Hutt

  • Panope worthingtoni Hutt.

  • Paphia curta (Hutt.)

  • *Pecten convexus Q. & G.

  • Pecten huttoni (Park)

  • Struthiolaria cincta Hutt.

  • Surcula aff. fusiformis (Hutt.)

  • Turbo aff. superbus Zitt.

  • Turritella semiconcava Sut.

  • Verconella nodosa var.; not Recent

  • Verconella aff. dilatata; fragment only

  • Voluta sp.; not Recent

[Footnote] * J. Park, Rep. Geol. Explor. during 1886–87, p. 173, 1887.

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There are only thirty-four species in this list, and many of them are represented by fragmentary material only, or they are filled with a hard and tough matrix. The hinge-teeth and apertures of many of the species are obscured, and this makes the identification a little uncertain. Only seven of the species are certainly Recent, and the percentage of Recent species therefore falls as low as 21. The small size of the collection, the fact that large species only were in a condition to be collected, and the uncertainty of identification in some cases make it unsafe to rely too closely on this percentage in correlating the strata with those of other localities in New Zealand.

The nature of the mollusca points rather to the Target Gully horizon, for there are only six species that do not occur there, and these species are found in horizons of much the same position near Oamaru or in the Trelissick Basin. On the other hand, the fauna of this stratum is of a distinctly older type than that of any of the coastal localities of the district in which we have collected fossils up to the present time.