Mimachlamys erycina, Dijkstra & Maestrati, 2010

Dijkstra, Henk H. & Maestrati, Philippe, 2010, Pectinoidea (Mollusca, Bivalvia, Propeamussiidae, Entoliidae and Pectinidae) from the Austral Islands (French Polynesia), Zoosystema 32 (2), pp. 333-358 : 348-350

Mimachlamys erycina n. sp.

( Fig. 4 G-L)

TYPE MATERIAL. — Rapa. BENTHAUS, stn DW 1894, 27°40’S, 144°22’W, 100m, holotype spm( MNHN 21383).— Same data, paratypes, 2 spm ( MNHN 21384).

TYPE LOCALITY. — Austral Islands,E of Rapa Island, 27°40’S, 144°22’W, 100 m (BENTHAUS, stn DW 1894).

ETYMOLOGY. — Latin erycinus, adjective meaning shell of Venus.

OTHER MATERIAL EXAMINED. — Marotiri. BENTHAUS, stn DW 1879, 27°55’S, 143°30’W, 52 m, 1 spm.

Récif Neilson. BENTHAUS, stn DW 1917, 27°03’S, 146°04’W, 50-60 m, 8 spms, 1 lv, 2 rv. — Stn CP 1922, 27°04’S, 146°04’W, 150-163 m, 1 rv.

Banc Président Thiers. BENTHAUS, stn DW 1926, 24°38’S, 146°01’W, 50-90 m, 4 spms, 3 lv. — Stn DW 1929, 24°39’S, 146°02’W, 350-370 m, 1 rv. — Stn DW 1932, 24°41’S, 146°02’W, 500-800 m, 1 rv. — Stn DW 1933, 24°41’S, 146°01’W, 500-850 m, 1 lv.

Banc Lotus. BENTHAUS, stn DW 1947, 23°49’S, 147°54’W, 120-150 m, 1 spm.

Tubuai. BENTHAUS, stn DW 1958, 23°20’S, 149°30’W, 80-150 m, 2 lv. — Stn DW 1961, 23°21’S, 149°34’W, 470-800 m, 1 rv.

Banc Arago. BENTHAUS, stn DW 1968, 23°23’S, 150°44’W, 100-120 m, 2 spms. — Stn DW 1977, 23°22’S, 150°44’W, 90-95 m, 2 spms. — Stn DW 1979, 23°22’S, 150°44’W, 176-340 m, 1 lv. — Stn DW 1985, 23°26’S, 150°44’W, 100-107 m, 2 spms.

Rurutu. BENTHAUS, stn DW 1995, 22°29’S, 151°22’W, 212-450 m, 1 lv. — Stn DW 2003, 22°28’S, 151°19’W, 250-330 m, 4 lv, 4 rv.

Rimatara. BENTHAUS, stn DW 2013, 22°39’S, 152°50’W, 80-93 m, 1 spm.

DISTRIBUTION. — Austral Islands, alive at 50-120 m depth.

DESCRIPTION

Shell small, up to c. 11 mm high, fragile, semitransparent, weakly inflated, circular, nearly equivalve, equilateral,left and right valve equally convex, auricles strongly unequal in size and shape, umbonal angle c. 95-100°, brightly coloured with creamy, yellow or orange, usually with some whitish small spots.

Prodissoconch c. 200 µm in height.

Left valve sculptured with 20-24 regularly spaced, radial riblets, commencing 1.5 mm from the umbonal top, and delicate, widely arranged scales (often eroded) on the riblets, and secondary radial rows of hollow sections on both sides of the riblets antero-laterally of disc. Intercalated antimarginal microsculpture prominent postero-laterally, nearly lacking antero-laterally.Interstices wider than riblets. Auricles with 3 or 4 scaly axial riblets, slightly more prominent on anterior. Hinge line straight.

Right valve similarly sculptured as left valve, although lacking the secondary radial sculpture of delicate vesicles. Anterior auricle with 5 or 6 scaly radial riblets. Antero-dorsal margin strongly denticulate. Posterior auricle narrow, with 3 or 4 spinous riblets. Byssal fasciole and notch well developed. Functional ctenolium with 4-7 teeth. Resilifer triangular. Internal plicae extending from central sector to ventral margin.

Dimensions of the holotype: H 8.9 mm, W 8.9 mm, D 2.1 mm.

REMARKS

Mimachlamys erycina n. sp. is morphologically closest to M. kauaiensis ( Dall, Bartsch & Rehder, 1938) , from Hawaii and the southwestern Pacific. It differs in size (up to 11 mm in height, vs 6.5 mm in M. kauaiensis ), in having fewer radial riblets (20-24, vs 24-27 in M. kauaiensis ), in lacking commarginal sculpture on the left valve (prominent antero-laterally in M. kauaiensis ), in having a delicate row of hollow sections on each side of the radial riblets of the left valve (lacking in M. kauaiensis ). Mimachlamys kauaiensis was formerly often placed in Chlamys or Laevichlamys ( Dijkstra1995a:57) , but is actually more appropriately classified in Mimachlamys ( Paulay 2003) .

Figures

FIG. 4. — A-F, Semipallium rapanense (Bavay,1905);A, B, external and internal views of the left valve;C, D, external and internal views of the right valve; E, details of the left valve;F, details of the right valve;G-L, Mimachlamys erycina n. sp.; G, H, holotype, external and internal views of the left valve; I, J, holotype, external and internal views of the right valve; K, prodissoconch of the left valve (SEM); L, details of the left valve (SEM). Scale bars: E, F, L, 1 mm; K, 100 μm.