Pholidotrope gloriosa, Herbert, 2012

Herbert, D. G., 2012, A revision of the Chilodontidae (Gastropoda: Vetigastropoda: Seguenzioidea) of southern Africa and the south-western Indian Ocean, African Invertebrates 53 (2), pp. 381-381 : 479-480

Pholidotrope gloriosa sp. n.

Figs 61 , 62

Etymology: From Latin gloriosa (famous, glorious); in reference to Îles Glorieuses, near which the type material was collected.

Description:

Shell: Trochiform, small, spire conical, base somewhat flattened (L/D=1.18); teleoconch of 5.5 whorls; initial whorls rounded, becoming more flat-sided with growth; suture narrowly indented; sculpture of spiral cords and lamellate axial pliculae; first whorl sculptured only by relatively widely spaced axial pliculae (13), second whorl with 16 axial pliculae and 2 developing spiral cords; third whorl with 17 axial pliculae and a third spiral cord developing at shoulder; fourth and fifth whorls with 3 strong spiral cords and 18 and 19 axial pliculae respectively; cords and pliculae subequal in strength, their intersections produced into scale-like nodules, those on shoulder cord somewhat more rounded; suture level with subperipheral cord; cord intervals wider than cords themselves, that between peripheral and subperipheral cord deep. Base with 4 spiral cords, progressively weaker toward centre; umbilicus narrowly patent in juvenile, but umbilical and parietal regions covered by a thin, smooth inductural callus spreading from aperture at maturity. Peristome markedly oblique, more or less in one tangential plane; aperture D-shaped; columella more or less straight, but with a distinct, roundly trigonal tooth near its base; outer lip internally thickened, its edge flaring outward; inner thickening with 10 ridge-like denticles, that nearest columella largest, creating a U-shaped notch between it and columella tooth; interior of aperture nacreous, labral denticles not extending internally as in-running spiral ridges; exterior of outer lip subterminally thickened by a low collabral varix.

Microsculpture ( Fig. 62A, B ): Early whorls with close-set, microscopic granules, vermiform spiral threads not evident; fine, prosocline, scratch-like marks on later whorls. Protoconch ( Fig. 62C ): White, globose and distinctly exsert, diameter ca 280 µm; surface worn, but with evidence of a fine, flocculent microsculpture; terminal lip convex. Colour: White.

Dimensions: Holotype, length 4.7 mm, diameter 3.9 mm.

Operculum, radula and external anatomy: Unknown.

Holotype: MADAGASCAR: NW of Madagascar, west of Banc du Leven (12.53°S 47.67°E), - 35–150 m, BENTHEDI Exped’n, st’n 5, dredged, 1977 ( MNHN 24656 ).

Paratype: MADAGASCAR: NW of Madagascar, west of Îles Glorieuses (11.487°S 47.303°E), - 250 m, rock dredge, BENTHEDI Exped’n, st’n 8, dredged, 19.iii.1977 ( MNHN 24657 ) .

Distribution and habitat: Known only from off north-western Madagascar, - 35–250 m, presumably on rocky substrata.

Remarks: The small size and conical profile of Pholidotrope gloriosa renders it distinctive amongst south-western Indian Ocean chilodontids. The only similar species, Perrinia konos , is more elevated, less coarsely sculptured and has less well-developed dentition at the base of the columella.

Figures

Fig. 61. Pholidotrope gloriosa sp. n., holotype (MNHN): (A) apertural view, length 4.7 mm; (B) oblique basal view into aperture; (C) side view showing subterminal external varix (arrow).

Fig. 62. Pholidotrope gloriosa sp. n., holotype: (A) granular juvenile microsculpture; (B) fine scratch-like microsculpture on last adult whorl; (C) protoconch. Bars all = 100 µm.