Lamellipecten aduncus n. sp.

(Fig. 3 F-K)

TYPE MATERIAL. — Rurutu. BENTHAUS, stn DW 1999, 22°25.1’S, 151°22.1’W, 270-500 m, holotype spm (MNHN 21381). — Same data, paratypes, 3 (MNHN 21382), 1 (MNHN 21401), 2 (ZMA Moll. 4.09.014).

TYPE LOCALITY. — Austral Islands, north of Rurutu, 22°25.1’S, 151°22.1’W, 270-500 m (BENTHAUS, stn DW 1999).

ETYMOLOGY. — From numerous commarginal curved lamellae on both valves (Latin aduncus, adjective meaning curved).

OTHER MATERIAL EXAMINED. — Marotiri. BENTHAUS, stn DW 1884, 27°54’S, 143°33’W, 570-620 m, 2 lv, 1 rv. — Stn DW 1885, 27°52’S, 143°33’W, 700-800 m, 1 rv.

Banc Lotus. BENTHAUS, stn DW 1945, 23°49’S, 147°42’W, 120-500 m, 1 lv, 1 rv.

Banc Arago. BENTHAUS, stn DW 1974, 23°24’S, 150°44’W, 450-618 m, 3 lv, 2 rv (paratypes: 3 MNHN 21382, 2 ZMA Moll. 4.09.014).

DISTRIBUTION. — Austral Islands, live taken at 270- 500 m depth.

DESCRIPTION

Shell up to c. 28 mm in height, fragile, compressed, right valve slightly more inflated than left valve, nearly circular, somewhat higher than wide, inequivalve, equilateral, auricles unequal in shape, nearly equal in size, umbonal angle c. 105°, inner surface somewhat irregularly, radially undulated, opaque whitish.

Left valve sculptured with widely spaced radial lirae, commencing at c. 2 mm from the umbonal margin with c. 10 in number, increasing with interstitial lirae to c. 20 on the central part of the disc and to c. 45 to the ventral margin. Closely spaced commarginal lamellae commence in early ontogeny at c. 0.5 mm from the umbonal margin and extend to the ventral margin, increasing to ventrally curled prominent lamellae, forming almost hollow sections on the lirae. Anterior auricle with two prominent radial lirae and closely spaced commarginal lamellae, posterior somewhat weaker sculptured with c. 6 radial lirae and commarginal lamellae.

Right valve similarly sculptured as left valve, although weaker with more irregularly, closer spaced radial lirae. Commarginal lamellae widely spaced on anterior auricle with c. 6 radial riblets, posterior auricle with very closely spaced commarginal lamellae and 2 or 3 radial lirae. Hinge line straight. Byssal notch shallow, byssal fasciole narrow, ctenolium and interior ribs lacking.

Dimensions of holotype: H 13 mm, W 13.1 mm, D 3.2 mm.

REMARKS

The commarginal lamellae on the left valve resemble the sculpture of Parvamussium undisonum, but other characters strongly differ (Table 3). Parvamussium undosum also has a prominent commarginal sculpture on the left valve, which is more closely spaced than in L. lamellosus, and the inner ventral apron of the left valve is very weakly undulated (L. lamellosus has a strongly undulated inner surface on both valves). Moreover, radial sculpture is lacking on the anterior auricle of the left valves (L. lamellosus has two prominent radial lirae).