Acteon herosae, Valdés, 2008

Valdés, Ángel, 2008, Deep-sea “ cephalaspidean ” heterobranchs (Gastropoda) from the tropical southwest Pacific, Mémoires du Muséum national d'Histoire naturelle 196, pp. 587-792 : 627-629

“ Acteon ” herosae n. sp.

Figs 19D, E, 20A, 21

TYPE MATERIAL. — Holotype MNHN 20303 and 5 paratypes MNHN 20304-20307, 1 paratype LACM 2985 .

TYPE LOCALITY. — Plateau Chesterfield-Bellona, Coral Sea, 19°45’S, 158°26’E, 205 m [CHALCAL 1: stn D 33] .

MATERIAL EXAMINED. — Coral Sea. CHALCAL 1: stn D 33, New Caledonia proper. LAGON: stn 367, Grand Récif Sud , Plateau Chesterfield-Bellona, 19°45’S, 158°26’E, 205 m, 1 dd, 22°37’S, 167°04’E, 105 m, 1 dd, paratype ( LACM 2985 ); stn 386, holotype ( MNHN 20303 ; Fig. 19D). 22°37’S, 167°09’E, 128 m, 1 dd, paratype ( MNHN 20306 ) .

North of New Caledonia. MUSORSTOM 4: stn DW 186 , Vanuatu. MUSORSTOM 8: stn DW 1101 , 15°04’S, 167°08’E, 19°07’S, 163°30’E, 190 m, 1 dd, paratype ( MNHN 20304 ) . — 205-210 m, 1 dd, paratype ( MNHN 20307 ; Figs 19E, 20A). BATHUS 4 : stn DW 914 , Grand passage, 18°49’S, 163°15’E , Fiji. BORDAU 1 : stn DW 1494 , 18°55’S, 178°29’W, 240-319 m, 600-616 m, 1 dd, paratype ( MNHN 20305 ). 1 dd, paratype ( MNHN 20308 ) .

DISTRIBUTION. — Collected from the Coral Sea , Fiji, New Caledonia and Vanuatu (Fig. 21), in 105-600 m.

DESCRIPTION. — Shell morphology. Length 13 mm, width 5 mm (holotype). Shell solid, oval, with convex sides (Fig. 19D). Body whorl very large, about 5/6 of the shell length. Spire very short, conical, with 3 whorls. Suture channeled. Protoconch flattened, about 1 whorl and 450 Μm in diameter (Fig. 19E). Umbilicus closed. Aperture long and wide, wider anteriorly and narrowing abruptly at about 1/2 its length. The aperture is about 4/5 of the body whorl length. The anterior end of the aperture is expanded into a very short lip. Columellar margin thickened, slightly oblique, with a single, small fold. Sculpture of a number of punctuated spiral grooves (Fig. 20A). The punctuations are large, oval,

FIG. 19. Shell morphology of species of “ Acteon ”. A, “ Acteon ” osexiguus n. sp., holotype MNHN 20313 (4 mm), ventral view, New Caledonia, BIOGEOCAL stn KG 241. B, “ Acteon ” aphyodes n. sp., holotype MNHN 20272 (15 mm), ventral view, Fiji, BORDAU 1 stn CP 1460; C, protoconch of paratype MNHN 20274, New Caledonia, BIOCAL stn DW 70, scale bar = 500 Μm. D, “ Acteon ” herosae n. sp., holotype MNHN 20303 (13 mm), ventral view, New Caledonia, CHALCAL stn D 33; E, protoconch of paratype MNHN 20307, Vanuatu, MUSORSTOM 8 stn DW 1101, scale bar = 300 Μm. F, “ Acteon ” comptus n. sp., holotype MNHN 20293 (7 mm), ventral view, BIOGEOCAL stn CP 260; G, protoconch of paratype MNHN 20296, New Caledonia, BIOGEOCAL stn DW 313, scale bar = 300 Μm.

almost rectangular, partially fused together within each groove. The grooves are separated by gaps that are wider than the grooves. Colour uniform shiny white.

Anatomy. Unknown. All shells collected lacked soft parts.

REMARKS. — “ Acteon ” herosae is easily distinguishable from other Indo-Pacific Acteonidae by its shell morphology, with a very short spire and long and wide aperture. Punctacteon kajiyamai Habe, 1976 from Japan, recently redescribed and illustrated by Hori (2000a), also has a short spire, but the aperture is shorter and narrower than that of “ A. ” herosae , and has several dark brown bands on the shell that are absent in “ A. ” herosae .

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

ETYMOLOGY. — Named for Virginie Héros (MNHN) for her invaluable assistance during processing the material, curation and preparation of the manuscript.