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 : 610-612

“ Acteon ” fortis Thiele, 1925

Figs 10E, F, 11A, 12

Acteon fortis Thiele, 1925: 259 , pl. 30, figs 10-11.

FIG. 10. Shell morphology and anatomy of species of Bathyacteon n. gen. and “ Acteon ”. A, Bathyacteon aequatorialis (Thiele, 1925) , (4.5 mm), ventral view, Tonga,BORDAU 2 DW 1553; B, protoconch, Wallis Island, MUSORSTOM 7 stn DW 601, scale bar = 500 Μm; C, same shell, sculpture, scale bar = 200 Μm; D, radula, Philippines, MUSORSTOM 3 stn CP 106, scale bar = 100 Μm. E, “ Acteon ” fortis Thiele, 1925 , (8.5 mm), ventral view, New Caledonia, MUSORSTOM 6 stn DW 442; F, same shell, protoconch, scale bar = 300 Μm. G, “ Acteon ” laetus Thiele, 1925 , (3 mm), ventral view, New Caledonia, BATHUS 4 stn DW 914; H, same shell, protoconch, scale bar = 500 Μm.

TYPE MATERIAL. — One syntype MNHB (here designated as lectotype) .

TYPE LOCALITY. — Nias Island , Indonesia, 1°47.1’N, 96°58.7’E, 660 m [ Valdivia : stn 203] .

MATERIAL EXAMINED. — Indonesia. The type material . — KA- 830, Secteur de Poindimié , 20°49’S, 165°19’E, 105-110 m, 1 dd. RUBAR: stn DW 15 , Kai Islands 05°17’S, 132°41’E, 212-221 m, Norfolk Ridge. SMIB 8 : stn DW 154-159 , Banc Kaimon-Maru, 1 dd. 24°46’S, 168°08’E, 235-300 m, 1 dd .

Coral Sea. MUSORSTOM 5: stn 263, Capel Bank, 25° 21’S, Loyalty Basin. MUSORSTOM 6:stn DW 442, 20°54’S, 167°17’E, 159°46’E, 150-225 m, 1 dd; stn 270, 24°49’S, 159°34’E, 223 200 m, 1 dd (Figs 10E, F, 11A).

m, 1 dd. Vanuatu. MUSORSTOM 8: stn DW 972, 19°22’S, 169°28’E, North of New Caledonia. MUSORSTOM 4: stn DW 150, Grand 487-507 m, 1 dd.

Passage, 19°07’S, 163°22’E, 110 m, 2 dd. Fiji. BORDAU 1: stn DW 1423, 17°08’S, 178°59’W, 402-410 m, New Caledonia proper. BATHUS 1: stn DE 697, Passe de Hien- 1 dd; stn DW 1465, 18°09’S, 178°39’W, 290-300 m, 1 dd.

ghène, 20°34’S, 164°58’E, 570-650 m, 1 dd; stn DW 706 , Passe Tonga. BORDAU 2 : stn DW 1567 , NW of Tongatapu, 21°02’S, SE de Ngoe , 21°42’S, 166°34’E, 247-252 m, 5 dd . — LAGON: stn 175°19’W, 351-356 m, 2 dd .

DISTRIBUTION. — Type locality near Nias Island , Indonesia, in 660 m. Material herein collected in the Coral Sea, Fiji, Indonesia, New Caledonia, Tonga and Vanuatu (Fig. 12), in 110-660 m.

DESCRIPTION. — Shell morphology. Length 9 mm, width 4 mm (lectotype). Shell solid, elongate, with convex sides (Fig. 10E). Body whorl large, about 3/4 of the shell length. Spire elongate, conical, with 3-5 whorls. Suture channeled. Protoconch globose, about 1.2 whorls and 450 Μm in diameter (Fig. 10F). Umbilicus closed. Aperture oval, wider anteriorly, and long, about 3/4 of the body whorl length. Columellar margin slightly thickened, with a small, simple fold. Sculpture of several punctuated spiral grooves (Fig. 11A). The punctuations are conspicuous, regularly oval, and situated next to each other within each groove. The grooves are separated by gaps that increase in width towards the posterior end of the spire. The 2 grooves near the suture are closer to each other again. Colour uniformly whitish.

Anatomy. Unknown. All shells collected lacked soft parts.

REMARKS. — “ Acteon ” fortis was originally described from material collected from Zanzibar, East Africa, and Nias Island, Indonesia. The original illustrations of this species (Thiele 1925: pl. 30, figs 10-11) show shells belonging to two different species. The shell from Zanzibar is shorter and wider, with a longer aperture, whereas the shell from Indonesia is longer with a much shorter, oval aperture. The only syntype remaining in the MNHB collection is the shell from Indonesia, which is here selected as the lectotype of “ A. ” fortis .

The additional material from the southwest Pacific here examined is similar to the lectotype of “ A. ” fortis and it is therefore assigned to this species. A definitive generic placement for this species is not possible until complete specimens become available for study.