Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)
(Pl. 47k): "the pinnacles" gully or a more westerly locality, between Kai Iwi and Castlecliff, Wanganui, Castlecliffian (GNS, from a private collection)
Beu & Maxwell (1990): Chapter 16; p. 348; pl. 47 k.
Synonymy: Opalia n. sp., Beu & Maxwell 1990, p. 348, pl. 47k.
Description: Moderately large for family (30-35 mm high), tall and narrow, with moderately well inflated whorls, simple oval aperture with a continuous thickened peristome, and almost smooth base bordered by a prominent, rounded, smooth cord that runs around suture of whole shell. Sculpture of prominent but wide, rounded, curved, indistinctly edged, slightly irregular axial costae, crossed by many very low, wide, closely spaced, rather indistinct spiral cords. No varices present. Entire surface microscopically pitted in regular spiral rows; pits are large and obvious on some costal surfaces on the last whorl. Protoconch not seen.
Comparison: The new species is unusual among New Zealand Epitoniidae, most of which have sculpture of high, thin, axial lamellae only (Epitonium) or with the addition of many narrow spiral cords (Cirsotrema). It is an uncommon and interesting addition to the New Zealand Castlecliffian fauna, and was apparently a Castlecliffian arrival. The regular microscopic pitting and low, wide axial costae leave little doubt that this is a species of Opalia (Kilburn 1985, p. 241, 266). It is not unlike the living southern Australian O. australis (Lamarck), but we have been unable to match the relatively low, wide, very closely spaced axial costae and weak spiral cords with those of any Australian living species. The most closely similar species appears to be Opalia (?Pliciscala) aglaia (Bartsch) (Kilburn 1985, p. 271, fig. 51, 52) from South Africa.
Distribution: Castlecliffian; Castlecliff, Wanganui, only; most specimens are from the Ototoka Siltstone Tongue member of Butler's Shell Conglomerate, but a few have been seen from higher in the section, possibly as high as Pinnacle Sand.
Cite this publication as: "A.G. Beu and J.I. Raine (2009). Revised
descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990). GNS
Science miscellaneous series no. 27."
© GNS Science, 2009
(Included with a PDF facsimile file copy of New Zealand Geological Survey Paleontological Bulletin 58 in CD version from: Publications Officer, GNS Science, P.O. Box 30368 Lower Hutt, New Zealand)