Rimula leptarcis, Simone, Luiz Ricardo L. & Cunha, Carlo M., 2014

Simone, Luiz Ricardo L. & Cunha, Carlo M., 2014, Taxonomical study on the mollusks collected in Marion-Dufresne (MD 55) and other expeditions to SE Brazil: the Fissurellidae (Mollusca, Vetigastropoda), Zootaxa 3835 (4), pp. 437-468 : 459-460

Rimula leptarcis new species

Figures 121–125

Types. Holotype MNHN 25329.

Type locality. Brazil. Espírito Santo; off Itaúnas, continental slope of Abrolhos, 18°56’S 37°52’W, 85–105 m (MD55 sta. DC82; Bouchet, Leal & Métivier col., 28/v/1987).

Diagnosis. Apex slightly curved, located in posterior 1/4 of shell length. Height 44% of length; width ca. 60% of length. Sculpture reticulated, composed by ca. 40 radial cords and concentric cords, both similar sized, forming delicate reticulation. Foramen approximately 23% of shell length; located between anterior and middle thirds of shell.

Description. Shell size 4.4 mm; tall, bluntly conical; height 44% of length. Pure white. Protoconch of one rounded whorl (Fig. 124); situated on right; smooth, glossy; of 210 µm. Foramen cuneiform (pointed anteriorly), width ca. 10% of length; located between anterior and middle thirds of shell length; ca. 10% of shell width, 23% of shell length; edges irregular (Figs 121, 123, 125). Groove anterior to foramen very narrow, flanked by pair of cords similar to neighboring cords. Profile curved ventro-posteriorly; middle third of dorsal surface somewhat straight, parallel to apertural plane; total angle (excluding planar middle region) ca. 80° (Figs 122, 124); beak in posterior ¼ of shell length (in dorsal view), between dorsal and middle thirds in lateral view. Sculpture of ca. 40 narrow radial cords (Figs 121, 122, 124); cords increasing in strength towards aperture; primary, secondary cords intercalating (Figs 122, 124); concentric cords regularly distributed, as wide as radial cords, except close to margin, with radial cords somewhat stronger; radial, concentric sculptures forming delicate reticulation composed of series of rectangular pits (each rectangle about twice as long as tall, longer axis parallel to shell edges); interspaces between cords twice cords’ width; ca. 60 concentric cords along cords close to median line. Selenizone well-marked, edges as tall as radial cords, twice as tall as foramen edges, projected dorsally, with sharp edges; lunules regular distributed (Fig. 125). Aperture planar (Fig. 122), outline elliptical, width ca. 60% of length; edges slightly undulating due to radial cords. Inner surface smooth, glossy (Fig. 123).

Measurements (in mm). Holotype: 4.4 by 1.9.

Distribution. Known only from type locality.

Habitat. Sandy bottoms with coralline red algae, 85–105 m (dead specimen).

Material examined: Type.

Etymology. The specific epithet is a contraction derived from the Greek arkys – arcys, meaning net, and leptos, meaning delicate; a noun in allusion to delicate reticulate sculpture of the shell.

Remarks. Rimula leptarcis differs from R. frenulata Dall, 1889 , from the central and northern Caribbean ( Farfante 1947: pl. 49), by the more oval basal outline, taller shell, stronger sculpture, and the more central and wider foramen. It differs from R. pycnonema Pilsbry, 1943 , by the more elongated shell, and by more abundant and the delicate radial and concentric sculpture. It differs from R. dorriae Farfante, 1947 , from Florida, in having much more delicate and denser radial sculpture, by the more demarcated selenizone, and by a more elongated outline. The generic attribution is based on the apex curved downwards, the narrow and elongated foramen, the presence of an anterior foramen furrow, and by the absence of a septum ( Pilsbry 1943, Farfante 1947).