Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)
(Pl. 46b): Castlecliff, Wanganui, Castlecliffian (GNS, old collection)
Beu & Maxwell (1990): Chapter 16; p. 342; pl. 46 b.
Synonymy: Lucina divaricata of Gray 1843, p. 257, not of Lamarck; Lucina (Cyclas) cumingi A. Adams & Angas, 1863, p. 426; Lucina dentata of Hutton 1884b, p. 525, not of Wood; Divaricella huttoniana Vanatta 1901, p. 184; Divaricella cumingii of Hutton 1904, p. 92; Divaricella notocenica King 1933, p. 353; Divalucina huttoniana; Divalucina cumingi, Dekker & Houd 1995, p. 2, fig. 20.
Description: Moderately large for family (26-47 mm long), almost circular, well inflated, with low, central umbones. Margins smooth. External sculpture of many prominent, low, wide, bevelled costae crossing faint commarginal growth lines at about 45°; costae bevelled ("terraced"), with narrow, sharply raised dorsal edges and wide, gradually descending ventral slopes, divaricating at a radial line slightly in front of centre of disc. Long, narrow, weakly defined lunule in front of umbo. Hinge narrow, dominated by long, wide ligamental nymph and groove, with central socket and 1 bifid cardinal tooth in each valve, and 1 or 2 low, short lateral teeth at anterior end of hinge. Anterior adductor scar long and narrow, descending parallel to pallial line; posterior adductor scar oval; pallial line wide, without sinus.
Comparison: Analysis of rib widths and frequencies by Wakefield (1976) demonstrated that all New Zealand Eocene to Recent specimens of Divalucina belong in one species. Although this species has long been known as Divaricella huttoniana, Dekker & Houd (1995, p. 2) showed that it is indistinguishable from the species named much earlier in eastern Australia, Divalucina cumingi (A. Adams & Angas). D. cumingi lives now all around New Zealand, deeply buried in sand or mud, from the outer edge of the intertidal zone to the bathyal zone, but most commonly in less than 10 m off sandy beaches, in anoxic black sediment (Luckens 1972b); the bevelled, divaricating ribs are used in burrowing into the sediment.
Distribution: Bortonian-Recent; Recent, eastern Australia (type of D. cumingi); Recent, New Zealand (type of D. huttoniana); "Otekaike, Oamaru" (Otekaike Limestone near Otekaike, possibly Trig Z, Otiake, Waitaki Valley, North Otago; Waitakian) (type of D. notocenica). Common in many near-shore shellbeds and in sandstone throughout the Cenozoic rocks of New Zealand, from Middle Eocene to Recent; living also throughout southern, eastern and northern Australia.
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)