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 : 622-625

“ Acteon ” profundus n. sp.

Figs 16G, 17D, 18

TYPE MATERIAL. — Holotype MNHN 20315 and paratype MNHN 20316.

TYPE LOCALITY . — Loyalty Ridge, 21°12’S, 167°00’E, 2190-2205 m [BIOGEOCAL: stn DW 321 ] .

MATERIAL EXAMINED. — Loyalty Ridge. BIOCAL: stn KG 89, 21°03’S, 166°56’E, 2070 m, 1 dd, paratype (MNHN 20316) . — BIOGEOCAL: stn DW 321 , 21°12’S, 167°00’E, 2190-2205 m, 1 dd, holotype (MNHN 20315; Figs 16G, 17D) .

DISTRIBUTION. — Collected only from New Caledonia (Fig. 18), in 2070-2190 m .

FIG. 16. Shell morphology of species of “ Acteon ”. A, “ Acteon ” cohibilis n. sp., holotype MNHN 20289 (7.5 mm), ventral view, New Caledonia, BATHUS 2 stn CP 760; B, protoconch of paratype MNHN 20292, Tonga,BORDAU 2 stn DW 1585, scale bar = 500 Μm. C, “ Acteon ” loyautensis n. sp., holotype MNHN 20309 (9 mm), ventral view, BIOCAL stn DW 70; D, protoconch of paratype 20312, Wallis Island, MUSORSTOM 7 stn DW 604, scale bar = 500 Μm. E, “ Acteon ” rhektos n. sp., holotype MNHN 20317 (6 mm), ventral view,BORDAU 2 stn DW 1553; F, protoconch of paratype MNHN 20320, Wallis Island, MUSORSTOM 7 stn DW 601, scale bar = 500 Μm. G, “ Acteon ” profundus n. sp., holotype MNHN 20315 (5 mm), ventral view, BIOGEOCAL stn CP 321.

FIG. 17. Shell sculpture of species of “ Acteon ”. A, “ Acteon ” cohibilis n. sp., sculpture of holotype MNHN 20289, BATHUS 2 stn CP 760, scale bar = 200 Μm. B, “ Acteon ” loyautensis n. sp., sculpture of paratype MNHN 20312, Wallis Island, MUSORSTOM 7 stn DW 604, scale bar = 200 Μm. C, “ Acteon ” rhektos n. sp., sculpture of holotype MNHN 20317, Tonga, BORDAU 2 stn DW 1553, scale bar = 200 Μm. D, “ Acteon ” profundus n. sp., sculpture of holotype MNHN 20315, New Caledonia, BIOGEOCAL stn CP 321, scale bar = 200 Μm. E, “ Acteon ” osexiguus n. sp., sculpture of holotype MNHN 20313, New Caledonia, BIOGEOCAL stn KG 241, scale bar = 100 Μm. F, “ Acteon ” aphyodes n. sp., sculpture of paratype MNHN 20274, New Caledonia, BIOCAL stn DW 70, scale bar = 100 Μm.

DESCRIPTION. — Shell morphology. Length 5 mm, width 3 mm (holotype). Shell solid, elongate, with convex sides (Fig. 16G). Body whorl large, about 1/3 of the shell length. Spire short, conical, with 2-3 short whorls. Suture deeply channeled. Protoconch eroded in all specimens examined. Umbilicus closed. Aperture short and narrow, wider anteriorly, about 3/4 of the body whorl length. Columellar margin conspicuously thickened, with no folds or teeth. Sculpture of several punctuated spiral grooves (Fig. 17D). The punctuations are small, regularly oval, and separated from each other within each groove. The grooves are separated by gaps that are several times wider than the grooves. The posterior 1/3 of the spire has no grooves, with the exception of one wide groove composed of very elongate and compressed punctuations situated by the suture on the posterior end of the spire. Colour uniformly whitish.

Anatomy. Unknown. All shells collected lacked soft parts.

REMARKS. — “ Acteon ” profundus is morphologically similar to Acteon amabilis Watson, 1883 , originally described from the Azores and the Canary Islands, eastern Atlantic, in 1830-2060 m (Watson 1883). Both species have elongate shells with a sculpture of small punctuate spiral grooves with a wider groove near the suture. However they differ in the presence of a gap with no spiral grooves on the posterior 1/3 of the spire of “ Acteon ” profundus, not present in A. amabilis , the presence of 2 wider grooves near the suture of A. amabilis , whereas “ A. ” profundus has only one, and the presence of a tooth or fold on the columellar margin of A. amabilis , absent in “ A. ” profundus. There are no other species of Indo-Pacific Acteonidae with a similar shell morphology to “ A. ” profundus.

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

ETYMOLOGY. — From the Latin profundus (deep), in reference to the deep sea habitat of this species.