Alvania stenolopha Bouchet and Warén, 1993

Gofas, Serge, 2007, Rissoidae (Mollusca: Gastropoda) from northeast Atlantic seamounts, Journal of Natural History 41 (13 - 16), pp. 779-885 : 812-813

Alvania stenolopha Bouchet and Warén, 1993

( Figure 17A–D )

Alvania stenolopha Bouchet and Warén 1993, p 644 , 653–655.

Type material

Holotype from ‘ Monaco’ sta. 703 (coll. H. Fischer), in MNHN.

Type locality

Off Flores, Azores (39 ° 219N, 31 ° 069W, 1360 m).

Material examined

Hyères— Seamount 2 sta. DW200, 1 sh. (jv.); sta. DW203: 7 sh. (2.00×1.32 to 2.08× 1.48 mm). Atlantis— Seamount 2 sta. DW 261, 53 sh. (1.76×1.24 to 2.12× 1.50 mm).

Description

Shell with a moderately high spire, quite thin, up to 2.1× 1.5 mm. Protoconch of 1.3–1.5 convex whorls; surface of larval whorls covered by minute spiral threads. Teleoconch of 2.75– 3 whorls, with a sculpture of narrow, widely separated axial ribs, crowded spiral threads and distinct spiral cords restricted to the abapical area. Ribs ca 17–23 on the penultimate whorl, with adapical termination hardly prominent along the suture, interrupted where abutting on the first spiral cord at the periphery and not extending on the abapical part of the body whorl; ribs becoming attenuated or disappearing on the body whorl where approaching the outer lip. Four to eight cords on abapical area of the body whorl, much narrower than the interspaces, decreasing in size towards the umbilical chink. Outer lip slightly prosocline, with a thin edge somewhat flaring but hardly thickened externally, not overrun by the spirals; smooth inside. Inner lip thin, overhanging a distinct umbilical chink. Shell colour white, translucent.

Remarks

Albeit there is a superficial resemblance, this species is easily distinguished from A. adiaphoros by having minute spiral threads instead of granules on the protoconch, narrower ribs, a more fragile shell with spiral microsculpture extending on the body whorl and an outer lip expanded outwards rather than thickened.

Warén and Bouchet (2001) reported specimens tentatively assigned to this species at several sites along the North Atlantic ridge in 650–1850 m depth, together with an egg capsule containing a single young in protoconch stage ready to hatch.

Figures

Figure 17. (A, B) Alvania stenolopha Bouchet and Warén, 1993, shells from Atlantis seamount, DW261 (1340 m), actual size 2.12 and 2.02 mm; (C) protoconch of a juvenile shell, same locality; (D) detail of microsculpture, same shell as (A); (E) Alvania macella n. sp., holotype (sh.) from Atlantis seamount, DW261, actual size 2.04 mm; (F) paratype (sh.), same locality, actual size 2.10 mm; (G) protoconch of the same paratype; (H) detail of microsculpture of the holotype. Scale bars: 100 Mm.