Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)
(Pl. 3h): holotype, GS10191, CH/f104, near Waitangi radio station, Chatham Island, Waipawan (?) (TM4771, GNS)
Beu & Maxwell (1990): Chapter 6; p. 92; pl. 3 h.
Synonymy: Corbula tophina Marwick 1928, p. 473
Description: Rather small for genus (length 6.5-8.5 mm), inequivalve, right valve somewhat higher than left but apparently only very slightly longer. Umbones very prominent, broadly rounded; umbonal ridge sharp in both valves forming well defined posterior areas. Sculpture of low, rounded commarginal ridges, typically missing over much of shell because of abrasion, similar in nature on both flanks and posterior areas. Hinge imperfectly known, right valve with a tubercular, tooth-like chondrophore some distance behind beak, fitting into corresponding socket on left valve. Other internal features unknown.
Comparison: Caryocorbula tophina is distinguished from other named New Zealand corbulids by its small size, its subequivalve shape, its prominent umbones and sharp umbonal ridges, and by having commarginal sculpture on the posterior area similar to that on the flanks. C. nitens (Otaian- Altonian, Pakaurangi Point, Northland) is closest, but is smaller and more elongate, and has less prominent umbones and finer commarginal sculpture. Corbulids are quite well represented in the New Zealand Cenozoic fauna, but only one species, Caryocorbula zelandica (Opoitian-Recent), is still extant. This has a recorded depth range of 0-90 m (Powell 1979, p. 428), but some fossil species of Caryocorbula seem to have extended down into deeper waters (c. 200 m).
Distribution: Waipawan (?), Red Bluff Tuff, sea-cliffs near radio station, Waitangi, Chatham Island (type) (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)