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 : 641

“ Acteon ” sp. 12

Figs 24D, 25

MATERIAL EXAMINED. — Loyalty Ridge. BIOGEOCAL: stn DW 313 , 20°59’S, 166°59’E, 1600-1640 m, 2 dd .

DISTRIBUTION. — Collected only from New Caledonia (Fig. 25), in 1600-1640 m .

DESCRIPTION. — Shell morphology. Length 4 mm, width 2 mm (largest specimen examined). Shell fragile, very elongate, with convex sides (Fig. 24D). Body whorl large, about 3/4 of the shell length. Spire long, conical, with 2 elongate whorls. Suture deeply channeled. Umbilicus small, partially covered by an extension of the columellar margin. Aperture long and narrow, wider anteriorly, about 2/3 of the body whorl length. Columellar margin thickened, slightly twisted, with no folds or teeth. Sculpture of 7 punctuated spiral grooves. The punctuations are small, elongate, and separated from each other within each groove. The grooves are separated by gaps that increase in width towards the posterior end of the spire. The most posterior groove, near the suture, is composed of more oval punctuations. Colour uniformly whitish.

Anatomy. Unknown. All shells collected lacked soft parts.

REMARKS. — “ Acteon ” sp. 12 is a clearly distinct species of Acteonidae because of a unique combination of several characters including the presence of an elongate shell, an umbilicus, a long spire with only 2 whorls and a small number of spiral grooves. It differs from “ Acteon ” profundus n. sp. (another species with small, fragile and elongate shells), in having a smaller number of spiral grooves and lacking a gap with no spiral grooves near the posterior end of the spire. “ Acteon ” sp. 12 is not named here because of the small number of specimens available for study.

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