Retusa lenis, Valdés, 2008

Valdés, Ángel, 2008, Deep-sea “ cephalaspidean ” heterobranchs (Gastropoda) from the tropical southwest Pacific, Mémoires du Muséum national d'Histoire naturelle 196, pp. 587-792 : 736-737

Retusa lenis n. sp.

Figs 75A, B, 76

TYPE MATERIAL. — Holotype MNHN 20419 and 4 paratypes MNHN 20420-20422, 3 paratypes LACM 3003 .

TYPE LOCALITY . — East coast of New Caledonia, Passe de Hienghu , 20°33’S, 165°00’E, 270-282 m [ BATHUS 1 : stn DW 688 ] .

MATERIAL EXAMINED. — New Caledonia proper. VAUBAN: stn ratype ( MNHN 20420 ) . — BATHUS 2 : stn DW 717 , Ile des Pins , 40, 22°30’S, 166°24’E, 250-350 m, 2 dd, paratypes ( MNHN 20421 ). 22°44’S, 167°17’E, 350-393 m, 1 dd, paratype ( MNHN 20422 ) .

— BATHUS 1: stn DW 688, Passe de Hienghu, 20°33’S, 165°00’E, Loyalty Ridge. MUSORSTOM 6: stn DW 442, 20°54’S, 167°17’E, 270-282 m, 2 dd, holotype (MNHN 20419; Figs 75A, B) and pa- 200 m, 2 dd, paratypes ( LACM 3003).

DISTRIBUTION. — Collected only from New Caledonia (Fig. 76), in 200-350 m.

DESCRIPTION. — Shell morphology. Length 2 mm, width 0.8 mm (holotype). Shell fragile, elongate, wider anteriorly and narrower posteriorly, with nearly parallel sides (Fig. 75A). In some specimens, including the holotype, the left side is slightly concave. Only 1 whorl visible, forming nearly the entire shell, except for a small visible portion of the spire. Apex deeply umbilicate (Fig. 75B), with the aperture lip 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 with an inconspicuous fold. Umbilicus closed. Sculpture of a number of faint, simple spiral lines crossed by growth lines. Colour uniformly whitish.

Anatomy. Unknown. All shells collected lacked soft parts.

REMARKS. — The shell morphology of Retusa lenis is similar to that of Retusa succinta A. Adams, 1862 , redescribed by Hori (2000c). Differences between these species include the presence of grey spiral lines and the more quadrangular shape of the shell in the latter. Additionally, R. lenis has a more developed aperture lip.

This species is placed in Retusa , based on the shell morphology, pending availability of complete specimens.

ETYMOLOGY. — From the Latin lenis (soft, smooth), in reference to the smooth, shiny shell of this species.