Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)
(Pl. 8e): GS9508, J40/f8803, McCulloch's Bridge, Kaiatan (GNS)
Beu & Maxwell (1990): Chapter 8; p. 118; pl. 8 e.
Synonymy: Lunatia suturalis Hutton 1877b, p. 597; Natica suturalis; Ampullina (Megatylotus) suturalis; Sulconacca suturalis
Classification: Naticidae: Poliniceinae
Description: Rather small for family (height 8 - 17 mm), globose, spire about 0.3 total height. Apex corroded in all known specimens, protoconch probably paucispiral and incompletely calcified. Teleoconch whorls about 4, sharply shouldered, with a narrow sutural shelf on early whorls, a concave sutural channel on later whorls. Outer edge of channel sharply defined. Last whorl globose, umbilicate. Spiral sculpture of ill-defined threads, strongest in sutural channel and umbilicus. Axial sculpture of weak growth lines. Umbilicus moderately large, bounded on outer edge by a shallow sulcus running from base of aperture, margined on inner edge by a low, rounded ridge. Aperture semilunular; inner lip oblique, almost straight, parietal callus rather thin, not spreading over umbilicus. Outer lip prosocline, inclined at about 20° to vertical.
Comparison: The various New Zealand species assigned to Friginatica (= Sulconacca Marwick, 1924) are very similar to one another, and because of considerable intraspecific variation in such characters as spire height, width of sutural channel and strength of circumumbilical sulcus, they are difficult to identify confidently. In particular, it is uncertain if F. prisca (Bortonian, Waihao Downs) is really distinct from F. suturalis, although topotypes of the former species are typically less globose and have a deeper, broader and more sharply margined sutural channel than McCulloch's Bridge shells. F. prisca and F. suturalis both have the outer lip retracted at the sutural channel so that it meets the suture almost at right angles this character distinguishes them from the widespread F. vaughani (Duntroonian-Tongaporutuan) in which the outer lip crosses the sutural channel at about 45°, turning into the suture only at the last moment.
Friginatica is most characteristic of middle to outer shelf or upper bathyal assemblages from Bortonian to Recent in New Zealand. The type species is a Recent form from south-eastern Australia.
Distribution: Kaiatan, "Waihao" (type) probably Waihao Greensand, McCulloch's Bridge where this is one of the most common molluscs; Kapua Tuff, Waihao River.
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)