[Abstract read, by permission of the Director of the N.Z. Geological Survey before the Wellington Philosophical Society, 28th November, 1928; received by Editor, 29th November, 1928; issued separately, 25th March, 1929.]

The object of this paper is primarily a description of the molluscan. fauna of Chatton, eight miles north of Gore, Southland. Field-occurrences and stratigraphical relations are not discussed as such a course would have entailed further delay of a paper promised long ago.

The material belongs to two collections. One was made as far back as 1913 by Mr. R. A. W. Sutherland, now of Wanganui, and was kindly donated by him to the Geological Survey about six years ago in the hope that it would be critically examined. Work has proceeded intermittently on the material as opportunity offered, and the present paper is largely a result of that work.

In 1925 the late Dr. J. Allan Thomson lent to the Geological Survey a large collection gathered by Mr. E. M. Christie, of Gore, who has since then added to his original material. My sincere thanks are due to these gentlemen for providing facilities to describe such an interesting molluscan fauna. The Dominion Museum specimens were prepared by Miss M. Mestayer with great care, and thus were preserved many fragile specimens which would otherwise have been lost.

To clear the ground for discussion of the affinities and age-equivalents of the Chatton fossils it is necessary to discuss Suter's record of 29 per cent. of Recent species Suter's list (1921, p. 95) was prepared from Mr. Sutherland's collection, and most of the manuscript labels are preserved, so that practically all of the indentifications can be cheeked.

It will be seen from the comparative list given below that the results of the re-survey are very different from the original. Suter's conception of fossil species was vague and inconsistent, so that his groups are in general far too wide to be of practical significance. The palaeontological evidence cited by Dr. Marshall (1917, p. 460, p. 465) is therefore badly based, though the Oligocene age allotted to the Chatton beds by him is probably correct.

Accurate correlation of the Chatton sands with other fossiliferous deposits of New Zealand is difficult because of the very large proportion of new species. The assemblage of genera, however, agrees much more closely with that of middle Tertiary faunas (Ototaran to Awamoan) than with early Tertiary ones. This might be claimed to be the result of environment rather than time; but the complete absence of archaic or older Tertiary elements such as Monalaria, Speightia, Aporrhaidae, and Avellanidae, definitely rules out the

Bortonian and Tahuian stages. The Waiarekan is known only from a relatively small fauna which lived in a somewhat unusual environment, for the fossils occur in the fine tuffaceous calcareous matrix of a coarse igneous conglomerate. The presence of Spirocolpus tophina (Marw.) at both Lorne and Chatton is the only strong connecting link between the two faunas.

Although the generic constitution agrees well with the Awamoan, the consistent differences in related species demand a considerable lapse of time for their development. The absence of such characteristic Awamoan species as Limopsis zealandica Hutton, Turritella (Maoricolpus) cavershamensis Harris, Nassarius socialis (Hutton), Comitas fusiformis (Hutton) is also noteworthy.

Dr. Finlay (1924, p. 534) has already shown from the rich faunas secured by him at Clifden, Southland, that the period of time between the Waiarekan and Awamoan stages, represented by Thomson's Ototaran and Hutchinsonian, was of relatively long duration. It is to the earlier part of this period, i.e., to the Ototaran, that the Clifden fauna probably belongs. Finlay (1924, p. 535) has also correctly drawn attention to the close resemblance of the Chatton fauna to that of the Wharekuri greensand. Many of the common species at both localities are strikingly similar, but yet show important differences of detail. These are differences which may be due to environment, although the time factor has not yet been disposed of.