Serrata gradata, Boyer, 2008

Boyer, Franck, 2008, The genus Serrata Jousseaume, 1875 (Caenogastropoda: Marginellidae) in New Caledonia, Mémoires du Muséum national d'Histoire naturelle 196, pp. 389-436 : 424

Serrata gradata n. sp.

Fig. 51

FIGS 49-52. 49, Serrata sinuosa n. sp., holotype MNHN 20625, southern New Caledonia, BIOCAL

stn DW 51, H 7.10 mm. 50, Serrata arcuata n. sp., holotype MNHN 20627, southwestern New Caledonia, BATHUS 4 stn DW 885, H 5.10 mm. 51, Serrata gradata . n. sp., holotype MNHN 20628, northern New Caledonia,BATHUS 4 stn DW 918,

H 5.20 mm. 52, Serrata simplex n. sp., holotype MNHN 20630,southern New Caledonia, BATHUS 2 stn DW 730, H 4.30 mm.

TYPE MATERIAL. — Holotype (dd) MNHN 20628 and 2 paratypes (dd) MNHN 20629 .

TYPE LOCALITY. — Northern New Caledonia, 18°49’S, 163°16’E, 613-647 m [BATHUS 4: stn DW 918] .

MATERIAL EXAMINED. — Northern New Caledonia. BATHUS 4: stn DW 918, 18°49’S, 163°16’E, 613-647 m, 3 dd (holotype, Fig. 51 and paratypes) .

DISTRIBUTION. — Northern tip of New Caledonia, at the latitude of the Grand Passage, shells in 613-647 m.

DESCRIPTION. — Shell subovate, solid, opaque. Protoconch paucispiral, wide, bulging, smooth. Spire tall, massive, turriculate. Aperture moderately widened, oblique. Base rather wide. Outer lip moderately thickened, subvertical, shoulder angled, protruding, outer margin wide, thick, stepped, inner edge faintly reflected over upper third, excavated below, with about 7 labial denticles, smaller than the interspaces. Four thick, straight columellar plaits, 2 lowest ones very oblique, third one slightly more prominent than others, uppermost one smaller, subhorizontal.

Colour dirty white (faded and abraded).

Dimensions: 5.20 x 3.00 mm.

Radula unknown.

REMARKS. — In its general outline, especially the presence of the turriculate spire and shouldered labrum, Serrata gradata resembles a species of Dentimargo . These characters separate it from all other New Caledonian species of Serrata . However, the subequal labial denticles and the excavated lower labrum are diagnostic characters of Serrata . It must be noted that a slightly stronger denticle is located in the antepenultimate position, just at the greatest width of the slightly reflected outer lip. Such a pattern is not found in Dentimargo , where the largest denticle, when it occurs, is uppermost.

ETYMOLOGY. — Latin gradatus (adj., graduated, stacked), referring to the turriculate shape of the spire.