Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)
(Pl. 21b): GS9500, J41/f8028, excavation for Oamaru Borough Council septic tank, South Oamaru, Altonian (GNS)
Beu & Maxwell (1990): Chapter 11; p. 196; pl. 21 b.
Synonymy: B. (Evarnula) protensum Powell 1929, p. 74
Description: Size moderate for genus (height 20 mm), broadly fusiform, spire 0.4 total height. Protoconch narrowly dome-shaped, of a little more than 2 smooth whorls. Teleoconch of about 5 whorls, subangled near middle on spire; last whorl excavated, with long, curved neck. Axial sculpture of prominent rounded costae reaching from suture to suture on early whorls but obsolete on ramp on later whorls, arid largely confined to periphery on last whorl, in some shells becoming obsolete on last quarter-whorl; 8-11 costae per whorl. Spiral sculpture of low, narrow cords with interstitial threads. Aperture ovate, siphonal canal long, open, bent to left and away from aperture. Inner lip callused, with small parietal tubercle and another at upper end of siphonal canal. Outer lip with thin leading edge, thickened behind by rounded varix, and bearing 9-13 narrow lirae within.
Comparison: Buccinulum protensum is possibly only a variant of the highly variable B. compactum (Altonian, Target Gully Shellbed) but is distinguished from it and from other mid-Cenozoic species by its slender shape and its relatively long siphonal canal, by the persistence of axial costae onto the last whorl, and by its relatively weakly armoured aperture. B. longicolle (Altonian, Clifden) was synonymised with B. protensum by Ponder (1971b, p. 276-277) but although the two species are similar in shape, B. longicolle consistently has a more strongly armoured aperture with three to five additional tubercles on the columella, and Beu & Maxwell (1990) regarded it as a distinct species.
Distribution: Altonian; Mount Harris Formation, Old Rifle Butts, Cape Wanbrow (type); Pukeuri; excavation for Oamaru Borough Council septic tank, South Oamaru (moderately common).
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)