Cylichna tanyumphalos, 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 : 661-663

Cylichna tanyumphalos n. sp.

Figs 34, 35C, D, G

TYPE MATERIAL. — Holotype MNHN 20359 and 12 paratypes MNHN 20360-20362, 1 paratype LACM 2991 .

TYPE LOCALITY . — Norfolk Ridge , 24°44’S, 168°07’E, 430-450 m [ BERYX 11 : stn CP 21] .

MATERIAL EXAMINED. — New Caledonia proper. VAUBAN: paratype ( MNHN 20361 ) . — BATHUS 2 : stn DW 717 , Ile des stn 40, 22°30’S, 166°24’E, 250-350 m, 1 dd, paratype ( LACM Pins, 22°44’S, 167°17’E, 350-393 m, 1 dd, paratype. — BATHUS 2991 ) . — BATHUS 1 : stn DW 654 , Passe du Cap Baye , 21°17’S, 3: stn DW 838 , 23°01’S, 166°56’E, 400-402 m, 1 dd, paratype 165°57’E, 237-298 m, 9 dd & lv, 1 of them destroyed to dis- ( MNHN 20362 ) .

sect the radula, paratypes (MNHN 20360; Fig. 35G); stn DW Norfolk Ridge. BERYX 11: stn CP 21, 24°44’S, 168°07’E, 430- 688, Passe de Hienghu, 20°33’S, 165°00’E, 270-282 m, 1 dd, 450 m, 1 dd, holotype (MNHN 20359; Figs 35C, D).

DISTRIBUTION. — Collected from New Caledonia (Fig. 34), in 282-430 m.

DESCRIPTION. — Shell morphology. Length 6 mm, width 2 mm (holotype). Shell fragile, elongate, narrow anteriorly, with nearly parallel sides (Fig. 35C). Only 1 whorl visible, forming nearly the entire shell. Apex rounded, with a deep umbilicus partially covered by the columellar margin (Fig. 35D), with the aperture lip rising from the left side and forming a short wing connected to the columellar margin. Anterior end of the shell elongate. Aperture as long as the shell, wider anteriorly and narrowing gradually at about 1/10 of its length and again at 1/5 of its length. Columellar

FIG. 35. Shell morphology and anatomy of species of Cylichna Lovén, 1846 . A, Cylichna consobrinoides Kuroda & Habe, 1952 , (14 mm), ventral view, Coral Sea, MUSORSTOM 5 stn 265; B, same shell, posterior view. C, Cylichna tanyumphalos n. sp., holotype MNHN 20359 (6 mm), ventral view, New Caledonia, BERYX 11 stn CP 21; D, same shell, posterior view. E, Cylichna grovesi n. sp., holotype MNHN 20352 (6 mm), ventral view, VAUBAN stn 40; F, same shell,posterior view. G, Cylichna tanyumphalos n. sp.,radula of paratype MNHN 20360, New Caledonia,BATHUS 1 stn DW 654, scale bar = 20 Μm. H, Cylichna grovesi n. sp.,radula of paratype MNHN 20356, New Caledonia, BATHUS 2 stn CP 743,scale bar = 20 Μm.

margin thickened. Columella with one fold. Umbilicus long and deep. Sculpture of faint growth lines. Colour uniformly dirty white.

Anatomy. The digestive system contains 3 smooth gizzard plates similar in shape and size. The radular formula is 16 x 2.1.1.1. 2 in a paratype from New Caledonia (BATHUS 1 stn DW 654). The rachidian teeth are broad, with several short denticles decreasing in size towards the laterals of each plate (Fig. 35G). There is a gap with no denticles on the centre of each rachidian tooth. The innermost lateral teeth are hook-shaped, with a long, strong cusp with 8- 10 denticles. The 2 outermost teeth of each row are much smaller, also hook-shaped and have small denticles.

REMARKS. — The shell morphology of this species differs from that of other Indo-Pacific members of the genus. The long umbilicus and the shape of the aperture, with 2 separate narrowings are its most distinctive features. Adamnestia teramachii Habe, 1954 from Japan, illustrated by Hori (2000b), also has a deep umbilicus but the shell is much shorter.

Cylichna tanyumphalos is assigned to the genus Cylichna because of the presence of 3 smooth and oval gizzard plates and a radula with a denticulate rachidian tooth and several hook-shaped and denticulate lateral teeth.

ETYMOLOGY. — From the ancient Greek tany (long) and umphalos (umbilicus), in reference to the long apical umbilicus of this species.