Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)
(Pl. 23a): GS11187, D45/f8824, Lill Sand, Clifden, Southland, Lillburnian (GNS)
(Pl. 23c): GS11187, D45/f8824, Lill Sand, Clifden, Southland, Lillburnian (GNS)
Beu & Maxwell (1990): Chapter 11; p. 215; pl. 23 a,c.
Synonymy: Glycymeris (Grandaxinea) finlayi Laws 1939a, p. 470
Classification: Glycymerididae: Melaxinaeinae
Description: Moderately large for genus (height 60-90 mm), relatively strongly inflated, subcircular to oval; posterior area narrow, distinctly depressed. Radial sculpture of 34-36 prominent, well spaced costae, 5 or 6 on posterior area much weaker than others, broadly triangular and sharp- crested proximally, becoming more rounded and subdued distally. Commarginal sculpture of very numerous, closely spaced growth lines, particularly noticeable on well preserved juvenile shells. Hinge rather heavy, more strongly arched on large shells than on smaller ones; ligamental area with closely spaced chevron grooves.
Comparison: Tucetona finlayi is distinguished from the widespread species T. laticostata (Tongaporutuan(?)-Recent; almost certainly = G. wairarapaensis, Nukumaruan) by its much better-defined posterior area and by having radial costae of triangular rather than rounded section. T. monsadusta (Waiauan, Burnt Hill and Weka Pass, North Canterbury) is rather poorly known, but the available material suggests that it differs from T. finlayi in having more inflated umbones and broader, rounded costae with much narrower (linear) interspaces. As far as can be judged from the inadequate description and the poor illustration of the type, T. aucklandica (Otaian, Waiheke Island) seems to have similar radial costae to T. finlayi, and may prove to be conspecific, and therefore to be an earlier name for this species.
Distribution: Altonian-Waiauan; cutting behind Clifden Racecourse, Southland, Waiauan (type); Clifden section from Long Beach Shellbed to Nissen Shellbeds, particularly common in the Lill Sand.
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)