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Genus Elachorbis Iredale, 1915.
Type: Cyclostrema tatei Angas.
Elachorbis duplicarina n. sp. (Figs. 43, 45, 46.)
Shell minute, almost planispiral. Whorls four, convex on spire, body-whorl bicarinate. Protoconch of 2¾ smooth whorls with first two showing but little increase in diameter. Sculpture of four smooth spiral cords on body-whorl above periphery. Interstices about equal to cords. Upper keel, marking periphery, high and sharp; lower keel not so strong but still well defined. Space between keels with 3 rather close spirals; base with about 7 spaced threads. Growth-lines extremely fine. Aperture subcircular, with blunt angles at the keels. Outer lip thin, oblique. Umbilicus wide, open, with a strong
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spiral which causes an embayment in the inner lip.
Holotype in collection of N.Z. Geological Survey.
Height, .8 mm.; diameter, 2 mm.
The classification under Elachorbis is only provisional, for the two strong keels are not present in that genus. The shell figured by Cossman [1918, pl. 2, figs. 51, 52, 53] as Tornus (Adeorbis) miobicarinatus Sacco, from the Miocene of Prance, has a strong resemblance in general characters.