Retusa famelica Watson, 1883

Valdés, Ángel, 2008, Deep-sea “ cephalaspidean ” heterobranchs (Gastropoda) from the tropical southwest Pacific, Mémoires du Muséum national d'Histoire naturelle 196, pp. 587-792 : 728-730

Retusa famelica Watson, 1883

Figs 71A, B, 72

Retusa famelica Watson, 1883: 338 .

TYPE MATERIAL. — One syntype BMNH 1887.2.9.2216-7 .

TYPE LOCALITY. — Levuka , Fiji, 22 m [Challenger] .

MATERIAL EXAMINED. — New Caledonia proper. BATHUS 1 : stn DW 674 , Grande Passe de Touho , 20°49’S, 165°19’E, 105-110 m, 5 dd; stn DW 677 , 20°49’S, 165°19’E, 96-109 m, 3 dd (Figs 71A, B). Fiji. The type material .

DISTRIBUTION. — Originally described from Levuka, Fiji, in 22 m (Watson 1883). Specimens herein collected in New Caledonia (Fig. 72), in 105-109 m.

DESCRIPTION. — Shell morphology. Length 2.5 mm, width 1 mm (largest specimen examined). Shell fragile, very elongate, wider anteriorly and narrower posteriorly, with nearly parallel sides (Fig. 71A). Only 1 whorl visible, forming nearly the entire shell, except for a visible portion of the top of the spire and the apex of the protoconch, which is partially embedded. Apex deeply umbilicate (Fig. 71B), with the aperture lip conspicuously rising from the right side. The aperture lip forms a rounded wing connected to the columellar margin. Anterior end of the shell rounded. Aperture as long as the shell, wider anteriorly and narrowing abruptly at about 1/4 of its length. Columellar margin slightly thickened. Columella simple, with no folds. Umbilicus closed. Sculpture of a number of strong, simple spiral lines crossed by conspicuous growth lines, more marked near the apex. Colour uniformly whitish.

Anatomy. Unknown. All shells collected lacked soft parts.

REMARKS. — Retusa famelica , originally described from Fiji, is an elongate species with a rounded and conspicuous wing on the right side of the apex and a strong sculpture of spiral lines crossed by growth lines, more marked near the apex (Watson 1883, 1886). Examination of the original type material and the detailed drawings and text of the redescription by Watson (1886) allowed a positive identification of the present material from New Caledonia.

FIG. 71. Shell morphology of species of Retusa Brown, 1827 . A, Retusa famelica Watson, 1883 , (2.5 mm), ventral view, New Caledonia, BATHUS 1 stn DW 677; B, same shell, posterior view. C, Retusa sulcata (Watson, 1883) , (6 mm), ventral view, Fiji, SUVA 2 stn DW 04; D, same shell, posterior view. E, Retusa crispula (Watson, 1883) , (4 mm), ventral view, New Caledonia, MUSORSTOM 4 stn CC 175; F, same shell, posterior view. G, Retusa waughiana Hedley, 1899 , (2 mm), ventral view; New Caledonia, BATHUS 1 stn DW 697; H, same shell, posterior view.

Retusa concentrica A. Adams in Sowerby, 1850, originally described from the Philippines and subsequently reported from Japan (Hori 2000c), is similar to Retusa famelica in shell morphology. However, Retusa concentrica is proportionately shorter and has the growth lines well marked along the entire shell.

Since the anatomy of this species is unknown, it is provisionally maintained in the genus Retusa until complete specimens become available for study.