PUSIA (VEXILLENA) CHOSLENAE

PUSIA (VEXILLENA) CHOSLENAE

(CERNOHORSKY, 1982) COMB. NOV.

FIGURE 20G – K

Vexillum choslenae Cernohorsky, 1982b: 109 – 111 View in CoL ; figs 1 – 6.

Type data

Holotype: AM 71368, Japan, Tosa , 128 m, 30.8 mm, probably lost.

Paratypes: Paratype 1, formerly in collection A. Choslen, current whereabouts unknown, type locality, 30.9 mm; paratype 2, AMS C – 133281 (formerly in AMS, at present housed in AM), New Caledonia, Isle of Pines , 22 ° 52 0 S, 167 ° 35.5 0 E, 370 m, bottom of large slabs of beach rock, 32.7 mm ( Fig. 20G, H) .

Material examined

New Caledonia: Typical form: EXBODI, station DW3850, 22 ° 18 0 S, 168 ° 44 0 E, 450 – 500 m, Banc Sud Durand, 1 lv (17.1 mm); EXBODI, station CP3826, 21 ° 52 0 S, 166 ° 51 0 E, 354 – 509 m, off Ounia, 1 lv, (15.85 mm); EXBODI, station DW3859, 22 ° 20 0 S, 169 ° 01 0 E, 350 – 388 m, Banc de l 0 Orne/Walpole, 1 lv (15.25 mm; Fig. 20I). Smooth form: EXBODI, station CP3826, 21 ° 52 0 S, 166 ° 51 0 E, 354 – 509 m, off Ounia, 2 lv (MNHN IM-2007-38378, 13.0 mm; Fig. 20K) GoogleMaps .

Diagnosis

Shell medium sized, elongate-fusiform (w / h 0.33 – 0.38; a / h 0.48 – 0.5), with orthoconoid spire and rather long, stout siphonal canal. Protoconch orange, conical, with four or more glossy gently convex whorls. Teleoconch of up to ten evenly convex whorls. Suture distinct, narrowly canaliculated. Sculpture of dense, rounded, orthocline ribs, well pronounced on spire whorls and usually vanishing later, with last adult whorl nearly smooth. Interspaces between axial ribs typically with distinct rounded cords; squarish deep interstices between cords clearly seen on spire whorls and becoming very faint on last adult whorl. Last adult whorl evenly convex in its upper portion; shortly constricted to straight, rather long and stout, widely open siphonal canal. Siphonal fasciole with six or seven flattened cords. Aperture elongate, its outer lip lirate within, notably drawn towards tip of siphonal canal, forming slight concavity in its abapical portion. Inner lip with four columellar folds, uppermost strongest, subsequently gradually weakening. Shell colour orange brown with a white peripheral band on the spire whorls and a second white band on the last adult whorl, white and dark brown axial streaks.

Radula ( EXBODI , station CP3826, 13.0 mm Fig. 20M): Radula exceeding 0.4 mm in length, 0.08 mm wide, formed by about 43 + rows. Rachidian tricuspidate, with rather narrow base and robust pointed cusps. Some rachidians bear a pair of very feeble intermediate cusps, situated in interspaces between the major cusps. Laterals sickle-shaped, unicuspidate. Buccal mass encloses a soft hitinous horseshoe-shaped jaw ( Fig. 20N).

Distribution and habitat

Japan and New Caledonia, in deep water.

Remarks

Pusia (Vexillena) choslenae shows notable variations in sculpture and also in shell proportions. The typical form, distributed from Japan to New Caledonia, is characterized by a well-developed cancellate sculpture, which becomes indistinct only on late teleoconch whorls of adult specimens; a specimen studied herein ( Fig. 20I) is closest in morphology to the holotype and paratype 1. A smooth form, represented by paratype 2 ( Fig. 20G, H) and a sequenced specimen (MNHN IM-2007-38378), is found off New Caledonia. In addition to a weakly developed sulpture with indistinct spiral elements, this form has a slightly acuminate spire and is overall slightly wider than the typical form; however, specimens of intermediate morphology, with well-developed sculpture, rather wide last adult whorl, and acuminate spire, are present in our material. Having at present sequenced only one specimen, we assume that the observed morphological disparity only represents within-species variation .

Typical Pusia choslenae resemble Pusia vicmanoui in shell proportions, sculpture, and colour pattern, but can be distinguished from Pusia vicmanoui by a rather weak sculpture on the last adult whorl and the morphology of the subsutural area, smooth in Pusia choslenae , but undulating in Pusia vicmanoui because of axial ribs slightly projecting adapically. Adult Pusia (Vexillena) choslenae can be easily distinguished from other Vexillena species by the smooth or weakly sculptured late adult whorls. Specimens of Pusia (Vexillena) choslenae from New Caledonia ( Fig. 20K) often show a more pronounced sculpture; however, this tends to vanish on late teleoconch whorls.

PUSIA (VEXILLENA) ELLISCROSSI ( ROSENBERG &