Acteon cf. nakayamai Habe, 1952

Valdés, Ángel, 2008, Deep-sea “ cephalaspidean ” heterobranchs (Gastropoda) from the tropical southwest Pacific, Mémoires du Muséum national d'Histoire naturelle 196, pp. 587-792 : 590-592

Acteon cf. nakayamai Habe, 1952

Figs 1A, B, 3

Acteon nakayamai Habe, 1952 a: 70-71, text fig. 2.

TYPE MATERIAL. — Holotype NSMT Mo 39806.

TYPE LOCALITY. — Moeshima , Kagoshima Bay, Japan (Pleistocene) .

MATERIAL EXAMINED. — Indonesia. KARUBAR: stn DW 28 , Kai Islands , 05°31’S, 132°54’E, 448-467 m, 1 dd; stn CP 38, Tanimbar Islands, 07°40’S, 132°27’E, 620-666 m, 1 dd (Figs 1A, B) .

DISTRIBUTION. — Reported from Tosa and Kagoshima Bays, Japan, in 100-200 m (Hori 2000a). Material herein collected in Indonesia (Fig. 3), in 467-620 m.

DESCRIPTION. — Shell morphology. Length 16 mm, width 9 mm (largest specimen examined). Shell solid, elongate, with almost parallel sides (Fig. 1A). Body whorl large; spire short, conical, with 4 whorls. Suture slightly channeled. Protoconch unknown. Umbilicus closed. Aperture wider anteriorly and narrower posteriorly, about 6/7 of the body whorl length. Columellar margin thickened, slightly oblique, with a small, simple fold. Sculpture of a number of punctuated spiral grooves (Fig. 1B). The punctuations are conspicuous, irregular, almost rectangular, and situated next to each other within each groove. The grooves are separated by gaps narrower than the grooves. Colour uniformly brownish.

Anatomy. Unknown. All shells collected lacked soft parts.

REMARKS. — The two shells here examined, collected from Indonesia, resemble the holotype of A. nakayamai , illustrated by Higo et al. (2001). The outline of the shell, sculpture, shape of the aperture and other conchological characters are very similar to those of the holotype. Therefore the material from Indonesia is tentatively assigned to A. nakayamai until more specimens from this region become available to allow a reliable comparison and positive identification.

Acteon nakayamai was originally described by Habe (1952a) based on Pleistocene material collected from Moeshima, Kagoshima Bay, Kyûshû, Japan. Subsequently Habe (1961) transferred it to the genus Punctacteon Habe, 1961 . A definitive generic placement for this species is not possible until complete specimens become available for study, and it is provisionally regarded as a member of Acteon , the genus to which it was originally assigned.

FIG. 1. Shell morphology and anatomy of species of Acteon Montfort, 1810 . A, Acteon cf. nakayamai Habe, 1952 , (16 mm) ventral view; Indonesia, KARUBAR stn CP 38; B, sculpture of shell, KARUBAR stn CP 38, scale bar = 300 Μm. C, Acteon ionfasciatus n. sp., holotype MNHN 20260 (30 mm), ventral view, Philippines, MUSORSTOM 3 stn CP 118; D, radula of paratype MNHN 20262, Philippines, MUSORSTOM 2 stn CP 44, scale bar = 50 Μm; E, protoconch of paratype MNHN 20263, Philippines, MUSORSTOM 3 stn DR 140, scale bar = 200 Μm; F, sculpture of same shell, scale bar = 200 Μm.

FIG. 2. Shell morphology and anatomy of species of Acteon Montfort, 1810 and Rictaxis Dall, 1871 . A, Acteon chrystomatus n. sp., holotype MNHN 20256 (5.5 mm), ventral view, New Caledonia, BATHUS 1 stn DW 687; B, protoconch of same shell,scale bar = 300 Μm; C, sculpture of same shell,scale bar = 200 Μm; D, radula of paratype MNHN 20257, New Caledonia,MUSORSTOM 4 stn DW 149,scale bar = 10 Μm. E, Rictaxis sanguinea n. sp., holotype MNHN 20270 (2.5 mm), ventral view, BORDAU 2 stn DW 1543; F, same shell, protoconch, scale bar = 200 Μm; G, same shell, sculpture, scale bar = 100 Μm; H, radula of paratype MNHN 20271, New Caledonia, SMIB 8 stn DW 146-147, scale bar = 50 Μm.