Alvania letourneuxi n. sp.

(Figs 5; 6; 49A; 53A; Tables 1; 2)

urn:lsid:zoobank.org:act: A14FC6C0-1612-4047-9680-667661FE88A5

TYPE MATERIAL. — Holotype. Tuamotu • dd (height 1.60 mm, width 0.95 mm, Figs 5; 6; 49A); Makemo, Passe Arikitamiro; 16°37’15”S, 143°33’50”W; 1-20 m; J. Letourneux leg.; MNHN-IM-2000-38703.

TYPE LOCALITY. — Tuamotu: Makemo, Passe Arikitamiro; 16°37’15”S, 143°33’50”W; 1- 20 m.

DISTRIBUTION AND SYMPATRY. — Alvania letourneuxi n. sp. is known from the South Pacific Ocean, in the Tuamotu Archipelago (Makemo) (Fig. 49A).

Alvania letourneuxi n. sp. is sympatric with Alvania parvimaculata n. sp. in the Tuamotu (Makemo) .

ETYMOLOGY. — Named after Jean Letourneux (Mahina, Tahiti), who collected the type material in the Tuamotu, for his continuous study of the Polynesian molluscs, and for having made materials from his collection available for this revision.

DIAGNOSIS. — Alvania with small shell (<2 mm height); protoconch paucispiral; spiral sculpture a little stronger than axial; two spiral cordlets starting after protoconch-teleoconch boundary; colouration uniform white.

DESCRIPTION OF HOLOTYPE

Shell (Figs 5 A-C; 6A; 53A)

Small for the genus, height 1.60 mm, width 0.95 mm, height/ width ratio 1.69, robust, ovate-conical.

Protoconch (Figs 5D, E; 6 B-D)

Paucispiral with nucleus intorted, of 1 convex whorl, height 0.250 mm, nucleus diameter 0.075 mm, first half whorl diameter 0.150 mm, maximum diameter 0.200 mm; with 5 small keels, interspaced by axial riblets, replaced by scattered on the last quarter of whorl. Protoconch-teleoconch boundary well marked, prosocline.

Teleoconch

Of 2.90 convex whorls, with suture impressed. Axial sculpture on the last whorl of 21 slightly prosocline ribs thinner than interspaces, gradually vanishing at the base. Spiral sculpture of equidistant cordlets slightly broader than axials, 7 on the last whorl, 3 above the aperture, one on suture line and 3 on the base. Cordlets II and III starting immediately after the protoconch-teleoconch boundary; cordlet I (subsutural) thinner, starting subsequently. Medium size, rounded tubercles at the intersections; interspaces quadrangular. Microsculpture of weak, minute spiral threads crossing the growth lines (Fig. 6B). Umbilical fissure absent. Aperture piriform, height 0.92 mm, height/aperture height ratio 1.74, peristome continuous and simple, external varix moderately thickened, outer lip sharp, smooth internally, prosocline.

Colour

Colouration uniform white.

Operculum and soft parts

Unknown.

VARIABILITY

A single specimen known. (See Table 1 and Appendix 1).

REMARK

See under A. parvimaculata n. sp. for detailed comparison.