Cylichna grovesi, 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 : 663-664

Cylichna grovesi n. sp.

Figs 35E, F, H, 36

TYPE MATERIAL. — Holotype MNHN 20352 and 36 paratypes MNHN 20353-20358, 1 paratype LACM 2992 .

TYPE LOCALITY. — South of New Caledonia, 22°30’S, 166°24’E, 250-350 m [VAUBAN: stn 40] .

MATERIAL EXAMINED. — New Caledonia proper. VAUBAN: stn CP 743, Passe de Boulari , 22°36’S, 166°26’E, 713-950 m, 7 dd stn 40, 22°30’S, 166°24’E, 250-350 m, 11 dd, holotype ( MNHN & lv, 1 destroyed to dissect the radula, paratypes ( MNHN 20356 ; 20352; Figs 35E, F) and paratypes ( MNHN 20353 ). — BATHUS 1 : Fig. 35H); stn CP 755, Passe de Dumbéa , 22°22’S, 166°14’E, stn DW 683 , Passe de Hienghu, 20°35’S, 165°07’E, 380-400 m, 5 495 m, 1 dd, paratype ( MNHN 20357 ); stn CP 760, 22°19’S, dd, paratypes ( MNHN 20354 ); stn DE 696, Passe de Hienghène, 166°11’E, 455 m, 1 dd, paratype ( LACM 2992 ) .

20°34’S, 164°57’E, 497-520 m, 11 dd, paratypes ( MNHN 20355 ); Fiji. BORDAU 1 : stn CP 1505, 18°12’S, 178°37’W, 420-450 m, stn DE 697, 20°34’S, 164°58’E, 570-650 m, 1 dd . — BATHUS 2 : 2 dd, paratypes ( MNHN 20358 ) .

DISTRIBUTION. — Collected from Fiji and New Caledonia (Fig. 36), in 350-713 m, live in 713-950 m.

DESCRIPTION. — Shell morphology. Length 6 mm, width 1.8 mm (holotype). Shell fragile, elongate, narrower anteriorly, with nearly parallel sides (Fig. 35E). Only 1 whorl visible, forming nearly the entire shell with the exception of a small visible portion of the spire. Apex flat, deeply umbilicate (Fig. 35F), with the protoconch partially visible and the aperture lip rising from the centre. Anterior end of the shell rounded. Aperture as long as the shell, wider anteriorly and narrowing gradually at about 1/6 of its length. Columellar margin conspicuously thickened. Columella with no folds. Umbilicus closed. Sculpture of a number of irregular and inconspicuous growth lines. These lines are much stronger at the apex of the shell. Colour uniformly dirty white.

Anatomy. The digestive system contains 3 smooth gizzard plates similar in shape and size. The radular formula is n x 1.1.1.1. 1 in a paratype from New Caledonia (BATHUS 2 stn CP 743). The rachidian teeth are broad, with several short denticles decreasing in size towards the laterals of each plate (Fig. 35H). There is a gap with no denticles on the

centre of each rachidian tooth. The innermost lateral teeth are hook-shaped, with a long and strong cusp with 8-10 denticles. The 2 outermost teeth of each row are much smaller, also hook-shaped and have small denticles.

REMARKS — Cylichna grovesi is clearly distinguishable from other species here described. The shell morphology, with a narrower anterior end of the shell, the apex deeply umbilicate, with the protoconch partially visible and growth lines stronger at the apex, constitute a unique combination of characteristics.

ETYMOLOGY. — Dedicated to Lindsey Groves (LACM), who helped with the curation of the material and provided constructive comments on the manuscript.