Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)
(Pl. 9u): GS329, G45/f8491, Pomahaka River, Duntroonian? (GNS)
Beu & Maxwell (1990): Chapter 10; p. 140; pl. 9 u.
Synonymy: Cerithium rugatum Hutton, 1873b, p. 11 (not of Carpenter, 1865, nor of Deshayes, 1864); Batillaria pomahakensis Harris 1897, p. 229 (new name for Cerithium rugatum Hutton, preoccupied); Batillona pomahakensis
Description: Size moderate for family (height 30-65 mm), cerithiiform, spire elevated. Protoconch not known; teleoconch of up to at least 12 whorls, larger specimens often severely corroded. Early whorls biangulate, one angulation at or slightly above middle on spire, the other less prominent, about halfway between upper angle and lower suture; on later whorls lower angulation decreasing in prominence, whorls becoming strongly medially angled. Last whorl with weak peribasal angulation and another of similar strength on upper part of strongly convex base. Axial sculpture of narrow, well spaced costae reaching from suture to suture and slightly tubercular at intersections with whorl angulations on early whorls, but tending to become restricted to peripheral tubercles on later whorls; 9-11 axials on penultimate whorl. Spiral sculpture consisting of narrow cords marking whorl angulations, those on base slightly nodulose, and fine threads on ramp and base and between cords. Aperture ovate; columella twisted to left anteriorly to form very short siphonal canal, concave above. Inner lip callused; outer lip thin, broadly concave from suture to lower basal angulation, straight below.
Comparison: Batillaria(?) pomahakensis differs from most other New Zealand cerithioideans in its relatively large size, its strongly medially angled teleoconch whorls and its prominent axial sculpture. B. hectori (Altonian, Porter River, Castle Hill Basin) is similar but has more prominent axial nodules and prominent basal cords. Both species were assigned to Batillona Finlay, 1927 by Finlay (1927b, p. 496) but they are not congeneric (or even confamilial) with the type species B. amara (see below). Their affinities are uncertain, but they are here provisionally placed in Batillaria.
Distribution: Duntroonian(?), Pomahaka Formation, Pomahaka River (type); Waikoikoi Stream.
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)