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Genus Gonimyrtea n. gen.
Type: Loripes concinna Hutton.
Shell subtriangular because of obscure ridge running from umbo to middle of anterior margin, and another to posterior margin which is angled below middle. Lunule broadly concave, not invading hinge area, and not interfering with development of teeth. Lateral teeth of right valve extremely weak, left valve with no true laterals, the lunular margin being slightly raised to function as one. Anterior adductor impression long and narrow.
The poor development of lateral teeth, the long anterior adductor, and the shape of the shell, readily distinguish this genus from Notomyrtea.
Finlay (1926, p. 461) has already noted the possibility of this distinction.
Gonimyrtea bucculenta n. sp. (Figs. 32, 33, 34.)
Shell subcircular, beaks slightly in front of middle, not prominent. Lunule lanceolate, well sunk, smooth. Escutcheon absent. A weak ridge runs to anterior margin from umbo forming weak, anterior wing. Sculpture of narrow, relatively high, very regular concentric ridges, 6 per millimetre, with much wider flat interspaces. Left
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hinge with two small cardinals diverging from under umbo, lunular margin raised to function as a lateral. Right hinge with single triangular cardinal and small anterior tubercle. Anterior muscle-impression long and narrow, posterior triangular. Interior of shell striated above pallial line. Valve-margins smooth.
Holotype in collection of N.Z. Geological Survey.
Height, 6 mm.; length, 6.5 mm.; inflation (1 valve), 2 mm.
Distinguished from the Recent and Pliocene P. concinna by the more orbicular shape, less prominent anterior and posterior marginal angulations and well spaced ribbing.