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Taxonomy
Mienerita debilis (Dufo, 1840)
Nomenclature
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Family: NeritidaeGenus: Mienerita Dekker, 2000
SUMMARY
A thin lightweight shell with a flared final whorl, thin lip, and a low to flat spire, sometimes eroded. There are numerous (approximately 30) thin spiral cords separated by shallow interstices. The cords have a beaded appearance under magnification as a result of axial growth striae and intervening ridges on the spiral cords. The shell has a flat or dull appearance. The aperture is large and generally a grayish white with a yellow stain around the outer lip and occasionally on the parietal shelf. The parietal shelf is flat and smooth with a straight columella. There are no teeth on the outer lip or columella. The operculum is gray with a light tan and white area around the nucleus and irregular tan blotches that extend around the outer rim. There are faint spiral growth lines and a solid pustulose covering of very small granules. The outer 2/3 of the outer surface of the operculum, along the lamellar edge, is light gray while the inner portion (above the apophysis) is a dark charcoal gray. The apophysis is moderately sized and strongly flared with very fine longitudinal grooves. It is swept back at 15° with a small nuclear tooth that develops into a protruding peg, very much like the peg found in the genus Neritina. There is no medial or lateral tooth, but there is a transparent and reddish-brown corneous lamella around the outer edge of the operculum from well below the nucleus to a position past the lateral terminus to just short of the apophysis. This strip almost completely circles the operculum from one side of the apophysis, around the operculum to the other side. There is no discernable periostracum. The shell has a dirty white, gray, or yellow base color with black spiral ridges. The black on the spiral ridges is usually intermittent but some specimens show solid black lines while others have a spiral-banded appearance.