Epicodakia sweeti ( Hedley, 1899 )

Glover, Emily A. & Taylor, John D., 2007, Diversity of chemosymbiotic bivalves on coral reefs: Lucinidae (Mollusca, Bivalvia) of New Caledonia and Lifou, Zoosystema 29 (1), pp. 109-181 : 140-142

Epicodakia sweeti ( Hedley, 1899)

( Figs 18B ; 20 )

Cardita sweeti Hedley, 1899: 495 , fig. 5.

Ctena transversa Dall, Bartsch & Rehder, 1938: 131 , pl. 35, figs 9-12.

Epicodakia sweeti – Paulay 2003: 233.

TYPE MATERIAL. — Cardita sweeti : holotype, 1 sh, L 13.9 mm, H 12.2 mm, T 4.2 mm ( NMV F 27464 C). Ctena transversa : holotype, off Waikiki , Oahu , Hawaiian Islands ( USNM 337409 ).

TYPE LOCALITY. — Funafuti Atoll, Tuvalu.

MATERIAL EXAMINED. — Koumac. 3 stn, 12-120 m, 3 v. Touho. 3 stn, 0-35 m, 8 v. Lifou. 9 stn, 0-30 m, 16 v. Other New Caledonia. LAGON, stn 383, Grand Récif Sud, 22°32’S, 167°13’E, 62 m, 1 v. — Stn 1104, secteur de Belep, 19°42’S, 163°59’E, 22 m, 1 v. Chesterfield Islands. CORAIL 2, stn DW 09, 20°53’S, 161°35’E, 62 m, 1 v. — Stn DW 60, 19°15’S, 158°57’E, 45 m, 1 v. — Stn DW 136, 19°31’S, 158°16’E, 37 m, 2 v. — Stn DW 144, 19°28’S, 158°23’E, 50 m, 2 v.

DISTRIBUTION. — Amirante Islands (Indian Ocean), Bali, Great Barrier Reef, Hawaii, Marquesas.

DESCRIPTION

Shell medium sized, white or yellowish; H to 17.0 mm, L to 18.3 mm, oval, longer than high, moderately inflated, T/L 0.27. Sculpture of about 40 closely-spaced, rarely bifurcate, radial ribs that become more widely-spaced, asymmetric and steeper to anterior. Ribs crossed by closely spaced commarginal lamellae, producing low, regular, rounded scales on summits of ribs ( Fig. 20F ). Lunule shallow, lanceolate, slightly asymmetrical, RV protruding. Ligament short, external. Hinge plate narrow, RV with 2 cardinal teeth, large posterior cardinal bifurcate, with single anterior and posterior lateral teeth. LV with 2 cardinal teeth, larger is bifurcate, and 2 anterior and posterior laterals. Anterior adductor muscle scar medium long, detached for half of length. Pallial line entire. Shell outside pallial line fluted from impression of ribbing, glossy, margin finely denticulate.

REMARKS

This species is similar in shape and hinge characters to E. consettiana but can be easily distinguished by the fewer and more prominent radial ribs. The other Epicodakia species from New Caledonia, E. nodulosa n. sp., has fewer ribs (around 20) than E. sweeti as well as distinctive nodulose scales.

From the original illustration, Lucina minuata Deshayes, 1863 (p. 20, pl. 3, figs 4, 5), from Réunion, appears similar to E. sweeti , but the figured specimen is not same as the putative type specimen (MNHN) which is a Ctena species resembling C. bella (also see Lamy 1921: 258).

Figures

FIG. 18. — Outline drawings of interiors of right valves of Epicodakia Iredale,1930 species:A, E. consettiana Iredale,1930; B, E. sweeti (Hedley, 1899); C, E. nodulosa n. sp. Not to scale.

FIG. 20. — Epicodakia sweeti (Hedley, 1899): A, B, holotype, Funafuti (NMV F27464C), exterior of right valve and interior of left valve; C, exterior of right valve, Grand Récif du Sud, New Caledonia, stn 383, 22°32’S, 167°13’E, 62 m (MNHN); D, detail of sculpture of C; E, F, interior of left and right valves of C; G, H, details of hinge teeth of D and E. Scale bars: A-C, E, F, 10 mm; D, 500 µm; G, H, 2 µm.