GNS Science

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

New Zealand Cenozoic Mollusca

Volutomitra inconspicua (Hutton, 1885)


(Pl. 8i): GS9508, J40/f8803, McCulloch's Bridge, Kaiatan (GNS)

Beu & Maxwell (1990): Chapter 8; p. 121; pl. 8 i.

Synonymy: Mitra inconspicua Hutton 1885b, p. 326; Vexillum apicicostatum Suter 1917, p. 27; Conomitra inconspicua; C. apicicostatum; Waimatea inconspicua; W. apicicostatum; Volutomitra (Waimatea) inconspicua, Beu & Maxwell 1992, p. 121

Type species of Waimatea Finlay, 1926, synonymised with Volutomitra H. & A. Adams, 1853 by Maxwell (1992, p. 135)

Classification: Volutomitridae

Description: Size moderate for family (height 16-23 mm), fusiform, spire about 0.4 total height. Protoconch small, dome-shaped, of about 1.5 smooth whorls. Teleoconch of up to 6.5 whorls, typically turned in towards suture to form narrow sutural shelf, last whorl contracted gradually to a moderately long neck. Axial sculpture when present, confined to first 2 or 3 whorls of most specimens but persisting onto 4th whorl of a few specimens, consisting of narrow costae with interspaces of similar width. Spiral sculpture on spire whorls of fine threads or striae, last whorl with up to 15 weak cords or threads on neck. Rest of shell typically smooth and polished. Aperture elongate, rather narrow; columella straight or gently convex, bearing 4 (in a few specimens 5) narrow plaits, the abapical one considerably weaker than others. Outer lip thin, gently sinuous, smooth within.

Comparison: Volutomitra amplexa (Bortonian, Waihao Downs and Pareora River) is smaller (height 8-10 mm), more slender and somewhat higher-spired than V. inconspicua. V. banksi (Pl. 27k) is very similar to V. inconspicua in overall appearance, but is much larger (height 27-55 mm) and has a larger protoconch. Cernohorsky (1981, p. 1000) classed Waimatea as a subgenus of Volutomitra, but the differences between these taxa are very slight; they were regarded as synonyms by Maxwell (1992, p. 135).

The fossil New Zealand species of Volutomitra seem to have lived at much the same depth as V. banksi (i.e. in the outer shelf or upper bathyal zones).

Distribution: Kaiatan, Waihao Greensand, McCulloch's Bridge (probable type locality of both M. inconspicua and V. apicicostatum); Kapua Tuff, Waihao River; Lorne; Point Elizabeth Beach, Westland; Melrose, Buller River. Common at McCulloch's Bridge, uncommon at other localities.

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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