GNS Science

Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)

New Zealand Cenozoic Mollusca

Aethocola (Neocola) demissa (Marwick, 1931)


(Pl. 30g): holotype, GS1242, Y16/f7414, Tutamoe Formation, Island Creek, Gisborne district, Waiauan (TM 6804, GNS)

Beu & Maxwell (1990): Chapter 13; p. 267; pl. 30 g.

Synonymy: Austrofusus (Neocola) demissus Marwick, 1931, p. 114.

Classification: Buccinulidae

Description: Rather small for genus (height c. 35 mm), bucciniform, spire 0.45 total height. Protoconch not known, but probably like that of A. (Neocola) alpha (Pl. 25b). Teleoconch of about 6 whorls, broadly shouldered at or noticeably below middle on spire, sutural ramp broad, steep and concave on later whorls, whorl sides sloping inwards; last whorl with weak subangulation on base, neck short, twisted. Axial sculpture apparently commencing as narrow costae reaching from suture to suture, but soon becoming obsolete on ramp; last whorl with prominent rounded nodules on periphery and low, elongate ridges on base and little or no connection between the 2 rows; 10-12 nodules or costae per whorl. Spiral sculpture of narrow, low cords with interstitial threads and threadlets, 3 on base noticeably stronger than those above and below, and slightly thickened where they cross axial ridges. Aperture ovate, moderately large, with a short, twisted, deeply notched siphonal canal; fasciole prominent, bordered above by a narrow ridge. Outer lip with distinct "stromboid notch" near anterior end; internal characters not known.

Comparison: Aethocola demissa is differentiated from A. alpha, beta and gamma (Pl. 25 b, c, d) by its larger size, its broader shell, its more strongly sloping whorl sides, its weaker basal subangulation, and its coarser peripheral nodules. A. demissa seems to be more closely allied to A. apudalpha (Pl. 21 j) and to an undescribed species from Ardgowan Shellbed, Oamaru and from Tommy's Creek, Upper Waipara River (both Altonian), differing from them mainly in having distinctly differentiated basal spiral cords. These three species apparently belong to a different group (lineage) from A. alpha, beta and gamma.

Distribution: Lillburnian-Waiauan; Island Creek, Waipaoa River (type) and other localities in Gisborne district.

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
ISBN 978-0-478-19705-1
ISSN 1177-2441
(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)


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