Argyropeza izekiana Kuroda 1949

Argyropeza izekiana Kuroda

Argyropeza izekiana Kuroda, 1949:76–79, fig. 1 [holotype: NSMT; type-locality: off Tosa, Shikoku, Japan, 100 m].

Argyropeza izekii [sic] Kuroda.—Habe, 1964:42, pl. 12: fig. 27 [mistakenly cited as fig. 26].

DESCRIPTION.—Shell: small, about 4.6 mm long, elongate, turreted, comprising 8–11 whorls about 1.53 mm wide. There are 8 flat-sided adult whorls that are impressed suturally. Apical angle of shell 35 degrees. Adult whorls with two spiral cords, one near top and the other at bottom whorl. Lower spiral cord sometimes weak. Spiral cords weakly beaded. One microscopic spiral cord on upper portion of whorl adjacent to suture. Shell sculptured with 12–14 axial ribs per whorl that form small sharp nodes where they cross spiral cords. Axial ribs strongest on first two whorls of teleoconch. Body whorl lacks axial ribs, nodes and has weak spiral sculpture. Suture well-defined, set off by sloping inferior and superior sutural ramp on each whorl. Protoconch I smooth, comprising one and one-half whorls; protoconch II, consists of two whorls, sculptured with spiral band of ovoid pustules adjacent to suture and with two spiral cords, the lower of which is formed of two fine, spiral lirae. Sinusigera sinus deep and narrow. Abrupt transition from protoconch to teleoconch marked by distinct change in sculpture. Former varix normally on right dorsal side of body whorl. Sculpture of body whorl comprises two weak, widely-spaced, spiral cords below which are 4–5 spiral lirae that grow weaker as they approach the anterior siphonal canal. Aperture ovate-circular, a little more than one-fourth the length of the shell. Columella straight and with weak parietal callus. Anterior siphonal canal short and broad, opening to left about 45° from the shell axis. Outer lip convex, smooth, thin, slightly sinuous. Anal canal indistinct. Periostracum very thin, pale tan. Shell vitreous, shining, white, chalky in dead specimens. Operculum concave and with circumference slightly bent to fit snugly into aperture of shell.

Animal (preserved): Head-foot small in relation to shell, flesh colored. Snout bilobed at tip. Tentacles wide, more flat than round, and each with large black eye at outer side of tentacle base. Intestine large, filled with large ovoid fecal pellets composed of fine sand. Anus close to mantle edge. Buccal mass large, filling much of snout.

Radula (Figure 6): Radular ribbon long, taenioglossate. Rachidian tooth quadrate in shape, concave at sides, slightly convex at tip. Cutting edge of rachidian tooth serrated with long, sharply pointed central cusp that has a tiny lateral denticle on each side of the median portion of cusp. Base of rachidian tooth slightly convex with sharp lateral projection at each side. Basal plate of rachidian tooth thick. Lateral tooth trapezoidal, laterally elongate and with slightly curved top that is serrated with 7–8 pointed cusps. First cusp small, second large, wide, and pointed, and remainder small and decreasing in size toward the lateral portion of tooth. Blunt longitudinal projection extends from lower mid-portion of basal plate. Base of lateral tooth slightly concave. Inner marginal tooth long, slender, curved, sharply pointed at tip, and serrated with 5–6 sharp denticles on inner side and 5 denticles on outer side. Outer marginal tooth same as inner marginal, but lacking denticles on outer surface.

ETYMOLOGY.—Named in honor of Mr. Izeki.

COMPARATIVE