Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)
(Pl. 15e): GS9806, F45/f9668, Shell Gully, Chatton, Duntroonian (GNS)
Beu & Maxwell (1990): Chapter 10; p. 160; pl. 15 e.
Synonymy: Cominista chattonensis Finlay 1926b, p. 244
Description: Size moderate for genus (height 25-35 mm), ovate, spire sharp, about half total height. Protoconch mamillate, of about 1.5 smooth whorls. Teleoconch of 6-7 whorls, obtusely angled below middle on spire, sutural ramp steep, slightly concave; last whorl only weakly excavated, anterior end rather broad. Axial sculpture of prominent rounded costae reaching from lower suture to shoulder angle on spire but obsolete on ramp; typically extending about halfway across base on last whorl, but reduced to elongate tubercles on periphery on some shells; 9-11 costae on penultimate whorl. Spiral sculpture of fine cords or threads over whole surface, but absent from much of many adult shells because of corrosion. Many shells with narrow spiral colour bands (pale orange as preserved), 6 on last whorl. Aperture large, ovate, columella bent to left below middle to form short, open, deeply notched siphonal canal; fasciole prominent, upper edge margined by narrow ridge, lower edge strongly projecting. Outer lip thin, smooth inside.
Comparison: Cominella chattonensis is similar to the Castlecliffian-Recent species C. (Josepha) glandiformis but is considerably larger and has a less strongly concave sutural ramp, fewer but stronger axial costae and a more strongly projecting fasciole. C. glandiformis is a scavenger living on rocks or on mud-flats in estuaries only, but its several close Cenozoic relatives seem to have occupied the more normal shallow marine environment now occupied by Cominella (Cominella) species.
Distribution: Duntroonian; Chatton Formation, Shell Gully, Chatton (type) (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)