Ilanga lauensis, Vilvens & Williams, 2020

Vilvens, Claude & Williams, Suzanne T., 2020, New species of Ilanga (Gastropoda: Trochoidea: Solariellidae) from the Indo-West Pacific, Zootaxa 4732 (2), pp. 201-257 : 249-251

Ilanga lauensis n. sp.

( Figs 26 A–L, Table 17, Key 2: 16)

Type material. Holotype (5.8× 10.2 mm) MNHN IM-2000-34411 . Paratypes: 4 MNHN IM-2000-34412 , MNHN IM-2000-34413 and 1 paratype NHMUK 20190465 (as listed below) .

Type locality. Fiji, Lau Ridge, Vanua Balavu Is., BORDAU 1, stn DW1440, 17°11’S, 178°43’W, 259–348 m.

Material examined. Fiji. MUSORSTOM 10: stn DW1374, 18°19’S, 178°06’E, 259–348 m, 2 dd . —BORDAU 1: stn DW1440, 17°11’S, 178°43’W, 190–308 m, 2 lv, 3 juv lv (with holotype IM-2000-34411 and paratype 1 MNHN IM-2000-34412 . — Stn DW 1464, 18°09’S, 178°38’W, 285–300 m, 3 lv, 1 dd sub, 9 dd juv . — Stn DW 1465, 18°09’S, 178°39’W, 290–300 m, 2 dd . — Stn DW 1494, 18°55’S, 178°29’W, 240–319 m, 5 lv, 2 dd sub . — Stn DW 1497, 18°44’S, 178°25’W, 335–350 m, 9 lv . — Stn DW 1506, 18°09’S, 178°37’W, 294–300 m, 2 dd, 1 dd sub, 1 dd juv . — Stn DW 1507, 18°09’S, 178°38’W, 255–290 m, 11 lv, 4 dd sub (with 3 paratypes MNHN IM-2000-34413 and paratype NHMUK 20190465 ).

Distribution. Fiji, 290–335 m (lv).

Diagnosis. Medium-sized Ilanga species with moderately depressed, conical spire, subangulate periphery, 4 spiral cords on first teleoconch whorl and 5 or 6 on second one, no or very weak subsutural pleats, broad subangulate umbilicus with a weak spiral cord at rim, without axial pleats around rim and 10–12 smooth thin spiral cords on umbilical shell walls.

Description. Shell: Medium size for genus (H up to 6.0 mm, W up to 10.3 mm), wider than high, conical, glossy; spire moderately depressed, height 0.52×to 0.58×width, 1.53×to 2.16×aperture height; periphery weakly subangulate; umbilicus broad and deep. Protoconch ca. 200–250 μm wide, 1.25 whorls, rounded, with a straight terminal lip. Teleoconch up to 4.6 convex whorls with a weak subsutural ramp on second whorl but absent on other whorls; no or very weak subsutural pleats; early teleoconch whorls with 4 and later 5–6 smooth spiral cords, vanishing on next whorls; last whorls smooth with hardly visible spiral threads near periphery. Suture weakly canaliculated on second whorl, impressed on other whorls. First teleoconch whorl convex, sculptured with 4 smooth spiral cords appearing immediately after protoconch; P1 and P2 slightly stronger than other cords; no subsutural ramp. On sec- ond whorl, S2 and/or S3 appearing; weak subsutural ramp with P1 at rim. On third whorl, spiral cords flattening and weakening, subsutural ramp disappearing; very weak subsutural pleats occasionally forming; narrow translucent subsutural spiral band. Last whorls nearly smooth, some faint spiral cords around periphery. Aperture rounded triangular; peristome incomplete; outer and inner lip thin; inner lip without obvious thickening against umbilical rim. Base convex, smooth, without axial pleats around umbilicus and with a thin, weak spiral cord bordering umbilical rim. Umbilicus broad (diameter 20–25% of shell width), central, with perspective to apex, with subangulate rim; slightly convex umbilical wall with 10–12 smooth, thin spiral cords, without clearly visible axial threads; umbilical shell walls of adapical whorls occasionally with weak axial pleats.

Colour: Teleoconch nacreous white with 3 bands patterned with brown, brownish orange or pinkish brown chevrons, median band narrower; base paler with an external band of regular brownish patches.

Operculum: Corneous, multispiral with central nucleus, light brown.

Remarks. See under Ilanga helicoides description.

Etymology. After the type locality, Vanua Balavu Island, belonging to Lau Archipelago ( Fiji).

Figures

FIGURE 26. Ilanga lauensis n. sp., Fiji, BORDAU 1. A–D. Holotype MNHN IM-2000-34411, stn DW1440, 190–308 m, 5.8×10.2 mm. E–H. Paratype 2 MNHN IM-2000-34413, 5.4×9.6 mm. I–L. Paratype 3 MNHN IM-2000-34413, 5.4×9.6 mm. Scale 5 mm.