Ilanga laevissima ( Martens, 1881 )

Vilvens, Claude & Williams, Suzanne T., 2020, New species of Ilanga (Gastropoda: Trochoidea: Solariellidae) from the Indo-West Pacific, Zootaxa 4732 (2), pp. 201-257 : 208-210

Ilanga laevissima ( Martens, 1881)

( Figs 4 A–I, Key 1: 3)

DNA ref: Ilanga laevissima ( Williams et al. 2013; Sumner-Rooney et al. 2016)

COI sequence data: GenBank Accession number: HF586293

Trochus laevissimus Martens, 1881: 65 . Type locality: South Africa, 33°59’S, 17°51’E, 50 fathoms (91 m).

Minolia (Machaeroplax) congener Sowerby, 1903: 223 , pl. 5, fig. 2. Type locality: South Africa, off Cape Infanta, at 82 miles, 40 fathoms (73 m).

Solariella nitens Thiele, 1925: 48 (14), pl. 1 (13), fig. 16. Type locality: South Africa, South-west of Cape Point, 34°33’S, 18°21’E, 318 m.

Ilanga laevissima — Herbert, 1987: 310–313 , figs 1–3, 34–50.

Type Material. Herbert (1987) suggested that a specimen labelled ‘possible type’ at the NHMUK 1903.7.27.69 is the one illustrated by Sowerby (1903: plate 5, fig. 1), but suggested that it was unlikely to be type material. A single specimen at ZMB was found to match the original description as suggested by Herbert (1987), and is here considered to be the holotype ( Trochus laevissimus ZMB /Moll 29315, S. Africa Gazelle 50 fms; Fig. 4 G–I).

Material examined. South Africa, Cape Province, NMDP (Africana): stn A 18178 D, 34°25’S, 24°00’E, 115 m, 2 lv ( NMSA V3139 ) . —Stn A 18994 D, 34°19.5’S, 23°30’E, 104 m, 1 lv ( NMSA V4397 ).—Local diver, False Bay , 50–60 m, 1 lv

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Distribution. South Africa, from Zululand to Atlantic Cape Province ( Herbert 1987), 60–350 m, lv at 50– 270 m.

Description (supplementary—based on the original description and specimens sequenced). Shell: Rather tall for genus (H up to 15 mm, W up to 22 mm), height 0.65–0.79×width, about 2.4×aperture height, wider than high, shape conical to slightly cyrtoconoidal, thin-shelled, glossy; spire moderately elevated; periphery rounded; umbilicus broad, deep. Protoconch ca. 300–350 μm wide, 1.25 whorls, rounded, with about 5 weak spiral threads on abapical part and straight, poorly visible terminal lip. Teleoconch of up to 5.8 convex, smooth whorls with weak subsutural ramp with rounded rim vanishing on last whorl; whorls nearly smooth (only very weak spiral on first whorls) with poorly marked growth lines. Suture canaliculated. Aperture subcircular; peristome incomplete; outer, inner lip thin; inner lip with basal thickening against umbilical rim. Base moderately convex, smooth. Umbilicus broad (diameter 20–25% of shell width), central, with perspective to apex, with subangulate to rounded rim, with or without axial pleats; convex wall with thin axial threads, without spiral cords.

Colour: Teleoconch greyish to yellowish white with variable brown flames, usually with two spiral bands, subsutural one whitish with regular brown spots, other whitish one at mid adapical half with brown chevron markings; base whitish with irregular, variable axial flames; protoconch white.

Operculum: Corneous, multispiral with central nucleus, brown.

Figures

FIGURE 4. A–F. Ilanga laevissima (Martens, 1881), South Africa, Cape Province, NMDP (Africana). NMSA V3139, Stn A 18178 D, 115 m. A–F. 8.5×12.3 mm. A–C. Shell, apertural, apical and basal views. D. Details of protoconch and first whorl. Scale 100 μm. E. Sculpture on whorls. Scale 1 mm. F. Details of umbilical area. Scale 1 mm. G–I. Holotype Trochus laevissimus ZMB/Moll 29315, S. Africa Gazelle 50 fms. J–L. Ilanga 18. South Africa, Cape Province, NMDP (Africana). NMSA V3139, Stn A 18178 D, 115 m. Although morphologically similar to I. laevisissima, this species is genetically distinct. 4.9×7.0 mm. Scale (except SEM images) 5 mm.