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 : 615-617

“ Acteon ” buccinus n. sp.

Figs 11D, 13B, C, 14

TYPE MATERIAL. — Holotype MNHN 20282 and paratype MNHN 20283.

TYPE LOCALITY . — North of New Caledonia, Grand Passage, 19°00’S, 163°18’E, 365 m [MUSORSTOM 4: stn CC 174 ] .

MATERIAL EXAMINED. — Coral Sea. MUSORSTOM 5: stn 346, Chesterfield Islands , 19°40’S, 158°27’E, 245-252 m, 1 dd, paratype (MNHN 20283; Figs 11D, 13C) .

North of New Caledonia. MUSORSTOM 4: stn CC 174, 19°00’S, 163°18’E, 365 m, 1 dd, holotype ( MNHN 20282; Fig. 13B).

FIG. 13. Shell morphology of species of “ Acteon ”. A, “ Acteon ” editus n. sp., holotype MNHN 20299 (10 mm), ventral view, MUSORSTOM 10 stn DW 1314. B, “ Acteon ” buccinus n. sp., holotype MNHN 20282 (10 mm), ventral view, MUSORSTOM 4 stn CC 174; C, protoconch of paratype MNHN 20283,Coral Sea, MUSORSTOM 5 stn 346, scale bar = 500 Μm. D, “ Acteon ” ringiculoides n. sp., holotype MNHN 20321 (11 mm),ventral view, New Caledonia, LITHIST stn DW 12; E, protoconch of paratype MNHN 20323, New Caledonia, SMIB 8 stn DW 166, scale bar = 500 Μm. F, “ Acteon ” boteroi n. sp., holotype MNHN 20279 (12 mm), ventral view, MUSORSTOM 4 stn CP 169.

DISTRIBUTION. — Known from New Caledonia and the Coral Sea (Fig. 14), in 252-365 m.

DESCRIPTION. — Shell morphology. Length 10 mm, width 5 mm (holotype). Shell thin, elongate, with convex sides (Fig. 13B). Body whorl large, about 2/3 of the shell length. Spire very elongate, conical, with 4 whorls. Suture channeled. Protoconch globose, about 1 whorl and 700 Μm in diameter (Fig. 13C). There is a small umbilicus partially covered by an extension of the columellar margin. Aperture short and narrow, wider anteriorly, about 3/4 of the body whorl length. The anterior end of the aperture is expanded into a conspicuous, rounded lip. Columellar margin thickened, slightly oblique, with a small, simple fold. Sculpture of a number of punctuated spiral grooves (Fig. 11C). The punctuations are small, oval, partially fused together within each groove. The grooves are separated by gaps that are several times wider than the grooves. Colour uniformly whitish.

Anatomy. Unknown. All shells collected lacked soft parts.

REMARKS. — “ Acteon ” buccinus is very similar to Acteon danaida Dall, 1881 , originally described from the Tortugas, in the Caribbean Sea, in 620 m ( Dall 1881). Differences between these two species include the presence of a conspicuous fold on the columella of “ A. ” buccinus that is absent in A. danaida . Also, the aperture of “ A. ” buccinus is shorter and the columella is more oblique.

Among the Indo-Pacific species, “ A. ” buccinus most resembles “ A. ” editus in shell morphology and sculpture. Differences between these two species are the wider aperture of “ A. ” buccinus with a more conspicuous tooth or fold on the columella, its more deeply sulcate suture and its more convex spire shape.

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

ETYMOLOGY. — From the genus name Buccinum Linné, 1758 , in reference to the shape of the shell of this species, which resembles that of a member of the Buccinidae .