Arxellia herosae , Vilvens, Claude, Williams, Suzanne T. & Herbert, David G., 2014

Vilvens, Claude, Williams, Suzanne T. & Herbert, David G., 2014, New genus Arxellia with new species of Solariellidae (Gastropoda: Trochoidea) from New Caledonia, Papua New Guinea, Philippines, Western Australia, Vanuatu and Tonga, Zootaxa 3826 (1), pp. 255-281: 267-269

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Arxellia herosae

n. sp.

Arxellia herosae  n. sp.

( Figs 3View FIGURES 1 – 9, 42– 51View FIGURES 42 – 51, Table 4)

Clade A, sp. 7 — Williams et al., 2013.

Type material. Holotype (7.0 x 7.2 mm) MNHN IM- 2009-28739. Paratypes: 2 MNHN IM- 2009-31843, IM- 2009- 28740), 1 NHMUK 20140008.

Type locality. Southern New Caledonia, Norfolk Ridge, Kaimon Maru Bank, NORFOLK 1, stn DW1679, 24° 43 ’S, 168 ° 10 'E, 298– 324 m.

Material examined. Norfolk Ridge. BIOCAL: stn DW66, 24° 55 'S 168 ° 22 'E, 505–515 m, 50 lv.— SMIB 8: stn DW148, 24° 56 'S, 168 ° 21 'E, 510 m, 6 lv, 3 dd sub, 2 dd juv.—Stn DW 152 –154, 23° 18 'S – 23 ° 19 'S, 168 °05'E, 305–367 m, 7 lv, 1 lv juv.—LITHIST: stn DW07, 24 ° 55 'S, 168 ° 22 'E, 504–530 m, 5 lv.— NORFOLK 1: stn DW1679, 24° 43 ’S, 168 ° 10 'E, 298–324 m, 4 lv (with holotype and paratype IM- 2009-31843).—Stn DW1680, 24° 45 ’S, 168 ° 10 'E, 385–392 m, 2 dd.—Stn DW1691, 24° 54 ’S, 168 ° 22 'E, 509–513 m, 11 lv (with paratypes MNHN IM- 2009-28740 and NHMUK 20140008)

Distribution. Norfolk Ridge, 324–510 m (living).

Description. Shell: Size moderate for genus (height up to 7.0 mm, width up to 7.7 mm), conical, only very slightly wider than high; height 0.9 –1.0x width, 2.7–3.1 x aperture height; periphery subangular. Protoconch paucispiral, diameter approx. 350 µm, rounded, with microscopic, crisp granules, and 5 thin, equally spaced, spiral threads; terminal lip straight, without varix. Teleoconch of up to 5.2 whorls; first two whorls convex, subsequent whorls almost straight, but final whorl more convex; shoulder oblique, becoming horizontal on later whorls, with angulate rim on early whorls; whorls with up to 8 spiral cords; cords thin and almost smooth on first two whorls; on subsequent whorls, adapical cords beaded to subgranular, abapical cords smoother. Suture canaliculate on early whorls, not so on final whorl. First whorl sculptured from start by 6 thin, more or less equally spaced spiral cords; P 1 develops rapidly at rim of shoulder; P 6 close to abapical suture; faint, close-set axial threads between cords. On second whorl, P 1 stronger than other cords, P 6 at abapical suture and axial threads evanescing. Prosocline axial folds develop at start of third whorl, stronger below suture, rendering P 1 subgranular; secondary cord S 1 (holotype) or S 4 (paratype MNHN IM- 2009-28740) arising at start or at end of whorl, remaining weak and thin at end of whorl; P 1 strongest; P 5 strengthening but still weaker than P 1, subgranular, forming suprasutural carina. On fourth whorl, cords other than P 1 and P 5 of similar in strength, weakly subgranular; P 6 emerging from suture, smooth to weakly subgranular, rapidly approaching strength of P 5; shoulder more or less horizontal, suture not canaliculate. On fifth whorl, S 1 when present (if not then P 2) stronger than other intermediate cords, subgranular. On last whorl, S 6 arises, smooth, together with P 5 and P 6 forming a tricarinate periphery; T 2 arising above P 5, rapidly resembling P 4; T 3 arising later between P 1 and P 2, beaded. Aperture subquadrate; peristome incomplete; edge of inner lip somewhat thickened; outer lip thinner, fusing almost at a right angle with thickened base of columella. Columella vertical, weakly concave adapically; basally with a small flange and with two callus lobes, one basal the other at mid-point, partially overlapping umbilicus. Base weakly convex, almost flat; outer part with 9–15 faint spiral cords, difficult to discern in some specimens, resulting in a smooth appearance; 4 strong, close-set, beaded cords surrounding umbilical rim, innermost cord twice as thick as penultimate cord, pleated by thick, axially elongate nodules. Umbilicus deep, narrow (diameter ca. 6–10 % of shell width), rim angulate; inner wall weakly concave to almost straight, with 3 thick axial folds within.

Colour: First two teleoconch whorls nacreous white; subsequent whorls nacreous pinkish-white; base nacreous white; protoconch white.

Remarks. Arxellia herosae  is a distinctive species characterised by its bi-lobed columella callus, relatively depressed spire, tricarinate periphery and few beaded to subgranular spiral cords.

Etymology. Named after Virginie Héros ( MNHN) whose enthusiasm, kindness and efficiency are highly appreciated by all malacologists collaborating with the MNHN.

TABLE 4. Arxellia herosae n. sp.: shell dimensions for type specimens.

          H/W H/HA H/TW
holotype MNHN IM-2009-28739   7.0 7.2      
    5.2 5.9      
    7.0 7.2      

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