Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)
(Pl. 26g): GS13811, D45/f311, middle Slip Point Siltstone, Clifden, Clifdenian (GNS)
Beu & Maxwell (1990): Chapter 11; p. 236; pl. 26 g.
Synonymy: Gemmula clifdenensis Powell 1942, p. 49
Classification: Turridae: Turrinae
Description: Rather small for subfamily (height 15-35 mm), narrowly fusiform, spire 0.6 total height. Protoconch narrowly conical, of 5 whorls, last 2.5 whorls with narrow, distant axial costellae, remainder smooth. Teleoconch of 7-8 whorls, sharply keeled at or slightly below middle on spire; sutural ramp steep, with slight subsutural fold; last whorl strongly excavated with moderately long neck. Axial sculpture of narrow, rather sharp peripheral tubercles, 20-24 per whorl. Spiral sculpture of a narrow cord on subsutural fold, 2 or 3 of similar strength on peripheral keel, and 3-6 finer ones between. A narrow cord appearing between periphery and lower suture during growth, in some shells becoming as strong as subsutural cord. An additional 2 prominent cords, typically stronger than other spirals, appearing on base of last whorl, with numerous much weaker ones below. Aperture ovate, with a moderately long, narrow siphonal canal. Outer lip thin with a deep, V-shaped anal sinus, its apex on peripheral keel, lirate within.
Comparison: Gemmula clifdenensis is very similar to G. kaiparaensis (Otaian-Altonian, Pakaurangi Point, Kaipara Harbour) and possibly not really distinct, but apparently has a narrower, more sharply projecting peripheral keel, sharper and more numerous peripheral tubercles (17-20 per whorl in G. kaiparaensis), and crisper spiral sculpture. Many species of Gemmula have basically similar sculptural plans and require careful examination of protoconch as well as teleoconch characters for discrimination.
Distribution: Altonian-Clifdenian; Slip Point Siltstone, Slip Point, Clifden, Clifdenian (type) (not uncommon); Fouraye Siltstone, Clifden (uncommon); north shore, Parengarenga Harbour (very 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)