GNS Science

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

New Zealand Cenozoic Mollusca

Borsonia mitromorphoides Suter, 1917


(Pl. 15r): "Wharekuri", Waitaki River, Duntroonian (GNS)

Beu & Maxwell (1990): Chapter 10; p. 163; pl. 15 r.

Synonymy: B. (Cordieria) mitromorphoides Suter 1917, p. 59

Classification: Turridae: Borsoniinae

Description: Size moderate for subfamily (height 18-23 mm), shape rather variable, some shells (including holotype) with lower spire than figured specimen. Protoconch mamillate, of c. 2 smooth whorls. Teleoconch whorls weakly shouldered below middle on spire; sutural ramp slightly concave; last whorl excavated, with short neck. Axial sculpture of very short costae or nodules between shoulder angle and lower suture, becoming obsolete on later part of last whorl; 9-10 per whorl. Spiral sculpture very subdued, subobsolete on ramp, of fine threads below. Columella slightly convex, bearing 2, or in a few specimens 3, plaits. Outer lip with moderately deep, U-shaped anal sinus on ramp.

Comparison: Borsonia includes fusiform or biconic turrids with a moderately deep, rounded anal sinus on the sutural ramp, and one or two (three in a few species) distinct columellar plaits. The genus has a sporadic record in New Zealand, from Bortonian to Clifdenian. Extant species are bathyal, but fossil species are mostly from moderately shallow-water facies.

Distribution: Duntroonian, Wharekuri Greensand, Wharekuri (type); head of Lake Waitaki (uncommon).

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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