GNS Science

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

New Zealand Cenozoic Mollusca

Calliostoma (Maurea) fragile Finlay, 1923


(Pl. 19j): GS9685, J41/f9499B, Pukeuri road cutting, Oamaru, Altonian (GNS)

Beu & Maxwell (1990): Chapter 11; p. 187; pl. 19 j.

Synonymy: C. suteri var. fragile Finlay 1923, p. 102; Venustas fragilis; Maurea fragilis; Calliostoma (sensu lato) fragile, Beu & Maxwell 1990, p. 187

Classification: Calliostomatidae

Description: Rather small for subfamily (height 10-12 mm), trochiform, spire 0.6 total height, almost straight-sided throughout most of growth, then slightly concave (i.e. coeloconoid). Protoconch of little more than 1 whorl. Teleoconch of 6-7 almost straight-sided whorls with very weakly marked suture, last whorl with sharply angled periphery, base lightly convex with shallow central depression. Axial sculpture of low, narrow, prosocline costellae confined to first 4 or 5 whorls, finely reticulating spiral cords and forming small beads at intersections. Spiral sculpture commencing as 2 fine threads, with a 3rd appearing above and a 4th, just above suture, during growth; penultimate whorl with 4 narrow cords, the lowest noticeably stronger than others; some shells with threads appearing between cords on last whorl. All spire spirals prominently beaded. Base with a narrow, moderately prominent cord near periphery with 1 or 2 weaker ones on either side, and 3 or 4 nodulose cords in middle, space between (about half diameter) smooth except for growth lines or bearing a few weak spirals. Aperture quadrate, nacreous within; columella strongly oblique, with a low denticle at base; inner lip with narrow nacreous band extending into axial depression.

Comparison: Calliostoma fragile is distinguished from other mid-Cenozoic species of Calliostoma by its slightly concave outline, its narrow spiral cords and the broad, smooth or weakly sculptured zone on the base.

Distribution: Altonian; Ardgowan Shellbed, Oamaru (type); Target Gully Shellbed, Oamaru; Pukeuri (not 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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