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 : 638-639

“ Acteon ” sp. 9

Figs 24A, 25

MATERIAL EXAMINED. — Loyalty Ridge. BIOGEOCAL: stn CP 260, 21°00’S, 166°58’E, 1820-1980 m, 1 dd.

DISTRIBUTION. — Single specimen collected from New Caledonia (Fig. 25), in 1820-1980 m .

DESCRIPTION. — Shell morphology. Length 7 mm, width 4 mm (single specimen examined). Shell solid, elongate, with convex sides (Fig. 24A). Body whorl large, about 4/5 of the shell length. Spire short, conical, with 3-4 whorls. Suture channeled. Umbilicus closed. Aperture long and narrow, wider anteriorly. The aperture is about 4/5 of the body whorl length. Columellar margin thickened, slightly oblique, with an inconspicuous fold. Sculpture of a number of punctuated spiral grooves. The punctuations are large, oval, separated from the next one within each groove; they become larger near the posterior end of the spire. The grooves are separated by gaps that are as wide as the grooves. Colour uniform pale grey.

Anatomy. Unknown. All shells collected lacked soft parts.

REMARKS. — “ Acteon ” sp. 9 is most similar to Japonacteon sieboldii (Reeve, 1842) in shell morphology and it is possible that they are the same species. However, the single shell examined was collected in 1820-1980 m, which is deeper than the known bathymetric range of J. sieboldii . Since the single shell lacked soft parts, it is not possible to determine whether these two species are the same and I provisionally separate “ Acteon ” sp. 9 as a different, unnamed taxon.

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

A B C

FIG. 24. Shell morphology of unidentified species of “ Acteon ”. A, “ Acteon ” sp.9,(7 mm),ventral view, New Caledonia,BIOGEOCAL stn CP 260. B, “ Acteon ” sp. 10, (6 mm), ventral view, Philippines,MUSORSTOM 2 stn DR 33. C, “ Acteon ” sp. 11, (6 mm), ventral view, Fiji, SUVA 2 stn BS 26. D, “ Acteon ” sp. 12, (4 mm),ventral view, New Caledonia,BIOGEOCAL stn DW 313. E, “ Acteon ” sp.13, (4 mm), ventral view, New Caledonia,BIOGEOCAL stn CP 232. F, “ Acteon ” sp. 14, (7 mm), ventral view, Tonga, BORDAU 2 stn DW 1549.