Acteon, Montfort, 1810

Valdés, Ángel, 2008, Deep-sea “ cephalaspidean ” heterobranchs (Gastropoda) from the tropical southwest Pacific, Mémoires du Muséum national d'Histoire naturelle 196, pp. 587-792 : 619-621

“ Acteon ” cohibilis n. sp.

Figs 15, 16A, B, 17A

TYPE MATERIAL. — Holotype MNHN 20289 and 3 paratypes MNHN 20290-20292, 1 paratype LACM 2981 .

TYPE LOCALITY . — Passe de Dumbéa , south of New Caledonia, 22°19’S, 166°11’E, 455 m [ BATHUS 2 : stn CP 760] .

MATERIAL EXAMINED. — New Caledonia proper. BATHUS 1 : paratype ( LACM 2981 ); stn CP 760, 22°19’S, 166°11’E, 455 m, stn DW 687 , Passe de Hienghu , 20°35’S, 165°07’E, 408-440 m, 1 dd, holotype ( MNHN 20289 ; Figs 16A, 17A) .

6 dd; stn DE 705, Passe du Cap Baye, 21°02’S, 165°38’E, 350- Loyalty Ridge. BATHUS 3 : stn DW 790 , le Mont J, 23°49’S, 400 m, 1 dd, paratype (MNHN 20290) . — BATHUS 2 : stn DW 169°48’E, 685-715 m, 3 dd .

754, Passe de Dumbéa, 22°23’S, 166°13’E, 577-780 m, 1 dd, Wallis Island. MUSORSTOM 7: stn DW 604, 13°21’S, 176°08’W,

415-420 m, 1 dd, paratype ( MNHN 20291). 173°57’W, 578 m, 1 dd, paratype ( MNHN 20292; Fig. 16B). Tonga. BORDAU 2: stn DW 1585, Vava’u Islands, 18°33’S,

DISTRIBUTION. — Collected from New Caledonia, Tonga and Wallis Island (Fig. 15), in 400-685 m.

DESCRIPTION. — Shell morphology. Length 7.5 mm, width 4 mm (holotype). Shell thin, oval to elongate, with convex sides (Fig. 16A). Body whorl large, about 3/4 of the shell length. Spire elongate, conical, with 3 whorls. Suture channeled. Protoconch globose, about 0.8 whorl and 600 Μm in diameter (Fig. 16B). Umbilicus narrow, partially covered by an extension of the columellar margin. Aperture short and wide, wider anteriorly and narrowing abruptly near its middle portion. The aperture is about 4/5 of the body whorl length. The anterior end of the aperture is expanded into a very short lip. Columellar margin thickened, with a single tooth. Sculpture of a number of punctuated spiral grooves (Fig. 17A). The punctuations are large, oval, and partially fused to the next one within each groove. The grooves are separated by gaps that are about as wide as the grooves. All grooves are of similar width with the exception of 2 wider grooves, composed of larger punctuations, next to each other near the posterior end of the spire. Colour uniformly dirty white.

Anatomy. Unknown. All shells collected lacked soft parts.

REMARKS. — “ Acteon ” cohibilis is most similar in shell morphology to “ Acteon ” ringiculoides n. sp., but these two species are easily distinguishable by the more elongate shell of “ A. ” ringiculoides in specimens of similar size. Also “ A. ” ringiculoides lacks an umbilicus, it has a shorter and straighter columella, and lacks wider spiral grooves near the posterior end of its spire.

A definitive generic placement for this species is not possible until complete specimens become available for study.

FIG. 15. Collection localities of species of “ Acteon ” in the southwest Pacific: °, “ Acteon ” boteroi n. sp. Z, “ Acteon ” cohibilis n. sp. •, “ Acteon ” loyautensis n. sp.

ETYMOLOGY. — From the Latin cohibilis (short, abridged), in reference to the wide and short shape of the shell of this species.