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

Arxellia herosae n. sp.

( Figs 3 , 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 DW152–154, 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, 2.7–3.1x 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; P1 develops rapidly at rim of shoulder; P6 close to abapical suture; faint, close-set axial threads between cords. On second whorl, P1 stronger than other cords, P6 at abapical suture and axial threads evanescing. Prosocline axial folds develop at start of third whorl, stronger below suture, rendering P1 subgranular; secondary cord S1 (holotype) or S4 (paratype MNHN IM-2009-28740) arising at start or at end of whorl, remaining weak and thin at end of whorl; P1 strongest; P5 strengthening but still weaker than P1, subgranular, forming suprasutural carina. On fourth whorl, cords other than P1 and P5 of similar in strength, weakly subgranular; P6 emerging from suture, smooth to weakly subgranular, rapidly approaching strength of P5; shoulder more or less horizontal, suture not canaliculate. On fifth whorl, S1 when present (if not then P2) stronger than other intermediate cords, subgranular. On last whorl, S6 arises, smooth, together with P5 and P6 forming a tricarinate periphery; T2 arising above P5, rapidly resembling P4; T3 arising later between P1 and P2, 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.

Figures

FIGURES 1 – 9. Arxellia new species, all holotypes except A. tenorioi. 1, A. trochos, n. sp., type species of Arxellia n. gen. 2, A. boucheti n. sp. 3, A. herosae n. sp. 4, A. helicoides n. sp. 5, A. tenorioi n. sp. 6, A. tracheia n. sp. 7, A. maestratii n. sp. 8, A. thaumasta n. sp. 9, A. erythrea n. sp. Scale bar = 5 mm.

FIGURES 42 – 51. Arxellia herosae n. sp., southern New Caledonia, Norfolk Ridge. 42 – 46, holotype MNHN IM- 2009 - 28739, Banc Kaimon Maru, 298 – 324 m [NORFOLK 1, stn DW 1679]. 42 – 44, shell, 7.0 x 7.2 mm. 45, details of protoconch and early whorls. 46, details of columella and aperture. 47 – 49, paratype NHMUK 20140008, Banc Eponge, 509 – 513 m [NORFOLK 1, stn DW 1691], 5.2 x 5.9 mm. 50 – 51, MNHN, New Caledonia, 505 – 515 m [BIOCAL, stn DW 66], 7.3 x 6.7 mm. Scale bars = 5 mm, except figs. 45, 46: 100 µm.

Tables

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

	TW	H	W	HA	H/W	H/HA H/TW
holotype MNHN IM-2009-28739	5.2	7.0	7.2	2.6	0.97	2.69 1.35
paratype NHMUK 20140008	4.7	5.2	5.9	1.9	0.88	2.74 1.11
paratype MNHN IM-2009-31843	5.0	6.9	7.7	2.2	0.90	3.14 1.38
paratype MNHN IM-2009-28740	5.2	7.0	7.2	2.4	0.97	2.92 1.35