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Verticordiidae.
? Verticordia neozelanica (Suter).
1873. Trigonia peotinata Lamk.: Hutton, Cat. Tert. Moll. and Ech. N.Z., p. 27.
1914. Suspend: Suter, N.Z. Geol. Surv. Pal. Bull. 2, p. 38.
1915. Trigonia neozelanica Suter, N.Z. Geol. Surv. Pal. Bull. 3, p. 50, pl. 5, fig. 3.
Hutton apparently identified his single specimen with the Recent Australian Trigonia largely because the shell is pearly. No further specimens have been collected. The exterior sculpture was concealed by matrix and the umbo and hinge, as noted by Suter, are missing. When the exterior had been laid bare, Suter gave the specimen a specific name, following Hutton's generic placing without comment. He considered the shell to be a left valve, thus treating the beaks as opisthogyrous, as they should be if the shell is a Trigonid. However, the right hand side of the disc shows no modified posterior area such as is invariably present in Trigonia, but the left side has a well marked radial depression, extending from the umbo to the ventral margin. This so closely resembles the posterior depression characteristic of many pelecypods that we are almost certainly dealing with the right valve of a prosogyrous shell. Certainly, Trigonia is ruled out, but until further evidence is available, the real affinities are uncertain. The pearly shell, cordate shape, and regular, strong, radial ribs suggest the Verticordiidae, though the size is much greater than usual.
Locality: Hampden Beach. (Bortonian Stage.)
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Verticordia densicostata (Marshall).
1919. Trigonia densicostata: Marshall, Trans. N.Z. Inst., vol. 51, p. 234, pl. 16, fig. 1.
1923. Verticordia densicostata: Marshall, Trans. N.Z. Inst., vol. 54, p. 117.
This species has already been transferred by its proposer, at the suggestion of Cossmann, from Trigonia, but as this appears only in a list, it is liable to be overlooked. Here, again, we have to deal with a single specimen, so poorly preserved that even the family affinities are uncertain. It was placed under Trigonia “merely in order that it may be possible to refer to it by name. … In the meantime, it may be said that the species does not belong to any other genus of Tertiary or Recent mollusca hitherto found in New Zealand.”
The sculpture of densicostata is similar to that of the preceding V. neozelanica, but the shape does not agree so closely. Since this may be due to distortion during consolidation or movement of the beds, and since both specimens come from the same locality, it is conceivable that only one species is concerned. More specimens, however, are needed to show the true affinities of these two shells. Only one posterior fragment of what is probably densicostata was collected by the writer.
Locality: Hampden Beach. (Bortonian Stage.)