Lamylucina gaini Cosel 2006, n. comb.

Lamylucina gaini (Lamy, 1920) n. comb.

(Figs 1; 2A; 4)

Phacoides (Lucinoma) gaini Lamy, 1920: 192-194.

TYPE MATERIAL. — The material present in MNHN on which the description of L. gaini n. comb. is based were not specifically designated as types, it consists of three right valves and one left valve from the Bissagos Archipelago (Guinea-Bissau) and one left valve from Conakry (Guinea), these were to be considered as syntypes. As Lamy (1920) did not give a precise type locality, and as the specimen from Conakry belongs to another species (described in the next entry), the most typical specimen, and not the two smaller, figured specimens, from the Bissagos Islands lot is here selected as lectotype, and the other specimens are paralectotypes. The type locality is the locality cited by Lamy for this lot.

TYPE LOCALITY. — Passage between Soga and Rouba, Bissagos Islands, Guinea Bissau.

OTHER MATERIAL EXAMINED. — Guinea. Nearshore continental shelf, SEDIGUI cruises, 9°03’N- 9°48’N, 17-39 m, most taken by bottom grab, some by dredge, RV André Nizery, X.1988, leg. R. von Cosel, V.1988, 13 lots, sh. and v. (all MNHN).

Ilha do Principe. Baia de Santo Antonio, entrance, 15 m, RV Calypso, Golfe de Guinée, stn P 14, numerous v. (MNHN). — Between Punta da Mina and Punta Novo Destino, 6 m, RV Calypso, Golfe de Guinée, stn P 7, 6 rv., 1 lv. (MNHN). — Praia de Santo Antonio, RV Calypso, Golfe de Guinée, stn P 22, 2 v. (MNHN).

Equatorial Guinea. 01°40’S, 09°25’E, 150 m, in sediment core, communicated by S. Gofas, 1 rv. (MNHN).

Gabon. Cap Esterias, Pointe Idolo, on sandbank, 14.XI.1988, leg. R. von Cosel, 1 small chipped rv. (MNHN).

DISTRIBUTION. — Senegal (Dakar) to Guinea (Sierra Leone border) and Gabon; Sao Tomé, Ilha do Principe.

DESCRIPTION

Shell small, 9-20 mm, rather thin but appearing solid, subcircular to circular, almost as long as high (length/height ratio 1.13-1.15), slightly inequilateral, equivalve, very compressed. Beaks just in front of the vertical midline. Anterior part broadly rounded, with a shallow inflexion between the middle part and the rounded corner to the antero-dorsal margin which is straight. Postero-dorsal margin slightly convex, posterior margin rounded, with a more or less indistinct, rounded postero-dorsal corner. Ventral margin well and evenly rounded.

Exterior with regular, fine and thin commarginal lamellae (about 40-55 in large specimens) which on the very early part are more closely spaced than on the disk. Interspaces smooth. Part of the lamellae becoming more lamellate to foliate on the anterodorsal and postero-dorsal margins. Postero-dorsal area separated by a rather broad and shallow radial depression. Antero-dorsal area small, delimited by a sharp groove which also separates the disk sculpture with commarginal ridges from the foliate sculpture.

Hinge plate moderately narrow, right valve with a single small cardinal tooth, no lateral. Left valve with one anterior and one posterior simple cardinal, no laterals. Lunule very short, broad and heart-shaped, somewhat assymmetrical, laterally slightly more prominent in the right valve, deeply inset; escutcheon long and extremely narrow, almost nonexistent. Anterior adductor scar small and narrow, with moderately long ventral part separate from the pallial line, this latter meeting the muscle impression almost in the middle. Inner margin of valves smooth.

Valves entirely white; periostracum not seen.

Measurements are provided in Table 1.

BIOTOPE

In fine, more or less muddy sand, from shallow water to about 30 m.

REMARKS

Lamylucina gaini n. comb. is characterized by the very flat valves, the commarginal lamellae with clearly defined interspaces which are broader than the lamellae, and the well marked prolongations of these lamellae on the antero-and postero-dorsal keel.