Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)
(Pl. 6c): holotype, Hampden Beach, North Otago, Bortonian (TM6852, GNS)
Beu & Maxwell (1990): Chapter 7; p. 110; pl. 6 c.
Synonymy: Cirsotrema kuriense Marwick 1942, p. 275 (as kuriensis)
Description: Size moderate for genus (height 25-30 mm), spire elevated. Protoconch not known. Teleoconch whorls strongly convex, sutures obscured by lateral extensions of costae; last whorl with well defined basal disc. Axial sculpture of prominent prosocline costae reaching from suture to suture on spire and across basal disc to fasciole on last whorl. Costae narrow with much wider interspaces on early whorls, but becoming relatively much broader with narrow interspaces on later whorls; costae composed of numerous lamellae fused together, rounded on crests, abapertural face slightly concave. Varices at irregular intervals, scarcely distinguishable from other costae on later whorls; 9-11 costae (including varices) per whorl. Spiral sculpture of 5 or 6 low, flatfish cords on spire whorls, considerably more prominent on costal crests than in interspaces, and very fine interstitial threads. Last whorl with additional strong cord marking edge of basal disc, and fine threads between costae on base. Aperture subcircular, heavily variced, basal lip truncate. Fasciole well marked.
Comparison: Probably most closely related to Cirsotrema caelicola (Altonian, Kakanui) but much smaller, having more closely spaced axial costae at a similar stage of growth and having more prominent spiral cords on the axial costae.
Distribution: Bortonian, Hampden Formation, Hampden Beach (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
(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)