Ilanga polygramma, 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 : 227-229

Ilanga polygramma n. sp.

( Figs 15 A–J, Table 6, Key 2: 12)

Archiminolia fulgens — Vilvens, 2009: 80–81 , figs 31–34 (part)

Type material. Holotype (4.4× 8.4 mm) MNHN IM-2000-34400 . Paratypes: 4 MNHN IM-2000-34401 and 1 NHMUK 20190461 as listed below .

Type locality. Indonesia, Kai Islands . KARUBAR, stn DW15, 05°17’S, 132°41’E, 212–221 m.

Material examined. Indonesia, Kai Islands . KARUBAR: stn DW01, 05°46’S, 132°10’E, 156–305 m, 4 lv, 1 lv juv . — Stn DW 15, 05°17’S, 132°41’E, 212–221 m, 15 lv, 5 lv sub, 2 lv juv (with holotype and paratypes) . — Stn DW 28, 05°31’S, 132°54’E, 448–467 m, 25 lv . — Stn DW 29, 05°36’S, 132°56’E, 181–184 m, 28 dd . — Stn DW 49, 08°00’S, 132°59’E, 206–210 m, 1 lv . — Indonesia, Tanimbar Islands . KARUBAR: stn CP80, 09°37’S, 131°02’E, 199–201 m, 1 dd .

Distribution. Indonesia, Kai Islands, 184–448 m, lv at 210–448 m; Indonesia, Tanimbar Islands, 199– 201 m.

Diagnosis. A rather small Ilanga species with a depressed, conical spire, a subangular periphery, 4 spiral cords on first whorl, weak subsutural pleats on median whorls, angulate umbilicus with numerous axial threads all around, bordered by a smooth spiral cord at rim and 7–9 spiral cords with very weak axial threads inside.

Description. Shell: Rather small size for genus (H up to 4.4 mm, W up to 8.4 mm), wider than high, shape conical, thin-shelled, glossy; spire rather depressed, height 0.52×to 0.60×width, 1.6x–2.4×aperture height; periphery slightly subangular; umbilicus very broad, deep. Protoconch 250–300 μm wide, 1.25 whorls, rounded, with a thin straight terminal lip. Teleoconch up to 4.4 slightly convex whorls, with weak shoulder on first whorls, with very thin smooth spiral cords on first whorls disappearing on next whorls. Suture weakly canaliculated on first whorls. First teleoconch whorl convex, sculptured by 4 thin, evenly spaced, spiral cords appearing immediately except P1 that appears later; P2 at edge of subangulate subsutural ramp. On second whorl, spiral cords disappearing after half whorl, P2 last one present; weak, low subsutural pleats appearing. On third teleoconch whorl, subsutural pleats ceasing near end of whorl; narrow translucent subsutural spiral band; subsutural ramp weakening but still present. Whole surface smooth on last whorls; subsutural ramp vanishing. Aperture subtriangular; peristome incomplete; outer and inner lip thin; inner lip with weak basal thickening against umbilical rim. Base moderately convex, smooth on outer part, with 30–35 axial pleats on inner third, reaching umbilical rim. Umbilicus broad (diameter 25–30% of shell width), central, with perspective to apex, with angular rim marked by a thin smooth spiral cord; straight, vertical wall with 7 to 9 smooth spiral cords, cords closer to each other on adapical part, with very weak axial threads.

Colour: Teleoconch background nacreous white, with axial, more or less regular pinkish flames on periphery and a subsutural, chevrons patterned, spiral band; base lighter, internal half without maculation; protoconch offwhite.

Remarks. Ilanga polygramma n. sp. is close to I. fulgens from the Philippines and Taiwan, but is larger (H up to 7.7 mm, W to 12.9 mm) at a similar number of whorls, has a slightly more elevated shape (height 0.53x to 0.66x width, instead of height 0.52×to 0.60×width here), a more rounded periphery, more clearly distinct thin axial threads on the whole surface of the whorls and lacks axial treads inside the umbilicus.

Etymology. Numerous (Ancient Greek: πολύς, πολλή, πολύ) and line (Ancient Greek: γραμμή, ής), used as a noun in apposition—with reference to the numerous spiral lines inside the umbilicus.

Figures

FIGURE 15. Ilanga polygramma n. sp., Indonesia, Kai Islands, KARUBAR. A–H. Stn DW15, 212–221 m. A–D. Holotype MNHN (IM-2000-34400), 4.4×8.4 mm. E–H. Paratype 1 MNHN (IM-2000-34401), 4.2×7.1 mm. I–J. Stn DW01, 156–305 m, 5.3×9.2 mm. Scale 5 mm.