Diagnostic Description

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Diagnostic Description

Description.—Shell moderately large, trochoid in shape, rather thin and light in structure, with conspicuous spiral ornamentation. Whorls 10, the last three increasingly convex, the earlier ones flat-sided. Initial angle of spire 54°, increasing as the whorls broaden and inflate, thus giving the spire a slightly concave profile. Periphery obtusely angular. Base convex, excavate in the umbilical region but not perforate. Aperture irregularly subquadrate, the outer lip with an anal sinus about one-fifth the circumference of the body whorl. The sinus and its fasciole lie somewhat below the midpoint between suture and periphery. The columellar margin of the aperture is thickened, and the columella is spirally coiled as demonstrated by radiographs of the shell. The sculpture consists of strong spiral cords, which are beaded where the fine axial riblets intersect them. With growth, the cords increase in both size and number, new cords appearing as faint raised lines between fully developed ones. On the body whorl near the aperture, there are eight major and three intercalary cords above the slit, three major and one intercalary between the slit and the peripheral cord. The maximum number of spiral cords on the base is 26, opposite the aperture; because of the nacreous umbilical area, the number is less (22 and one intercalary) immediately behind the aperture. The ground color is cream white, with irregular axial streaks and flames of rusty red. Most of the beads on the spiral cords are pale, but the dark streaking covers even these in some places. The nacreous interior of the aperture and umbilical area are brilliantly iridescent. The operculum is almost circular, 12 mm in diameter, multispiral, each whorl with a conspicuous free margin.” (Bayer, 1963)


Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© Gillevet, Emilia

Source: Pleurotomariidae

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