Propeamussium andamanicum (E.A. Smith, 1894)

Dijkstra, H. H. & Maestrati, P., 2015, Pectinoidea (Bivalvia: Propeamussiidae and Cyclochlamydidae) from the southwestern Indian Ocean, African Invertebrates 56 (3), pp. 585-585 : 587-588

Propeamussium andamanicum (E.A. Smith, 1894)

Fig. 1C, D

Amussium andamanicum Smith, 1894: 172 , pl. 5, figs 13–14; Knudsen, 1967: 273, pl. 1, fig. 22, text-fig.

15. Type locality: Andaman Sea (12°59'N 93°23'10"E), - 1249 m, live, blue mud, 13.xi.1890

( Investigator , stn 113).

Propeamussium andamanicum: Dijkstra 1995: 15 , figs 5–8, 138–142; 2001: 74; Dijkstra & Maestrati 2008:

79; 2012: 391.

Description: Shell fragile, up to 58 mm high (most specimens smaller, up to 40–50 mm), hYaline, elongate, inequivalve, almost inequilateral, left valve slightlY more inflated than right valve, auricles small and almost similar sized, umbonal angle 105°–110°, left valve transparent white, right valve creamy. Interior riblets commencing directly below umbo, variable in length and number (most specimens 9–11), all gradually enlarging, lateral ones more prominent, extending to central shell disc. Prodissoconch 250 µm high. Byssal notch lacking. Left valve covered with fine commarginal lirae commencing on central shell disc, extending to ventral margin.Auricles rather small, equally sized and smooth, hinge line straight. Right valve with fine commarginal lirae, interstitial granulated (prismatic calcite layer).Auricles with delicate commarginal striae, anterior and posterior margin somewhat raised. No ctenolium. Resilifer rather triangularly elongate.

Type material examined: Lectotype (pr) ZSI 7418/9, designated by Dijkstra (1995: 15).

Other material examined: NW MADAGASCAR: (13°46'S 47°33'E), - 1490–1600 m, live, campaign Crevettière 1975, stn CH131, trawled, leg. A. Crosnier, 20.i.1975 ( NMSA J1599 ) . MOZAMBIQUE CHANNEL: (17°50'S 43°07'E), - 1475–1530 m, live, campaign Crevettière 1975, stn CH 126, trawled, leg. A. Crosnier, 16.i.1975 ( MNHN); (18°00'S 43°00'E) , - 1715–1750 m, live, campaign Crevettière 1975, stn CH 127, trawled, leg. A. Crosnier, 16.i.1975 ( MNHN) .

Distribution and habitat: Propeamussium andamanicum is recorded from the Andaman Sea, Laccadive Sea and Arabian Sea (Smith 1895, 1904), Gulf of Aden and Zanzibar area ( Knudsen 1967), New Caledonia (Dijkstra 1995), Vanuatu, Wallis and Futuna ( Dijkstra 2001), Fiji ( Dijkstra & Maestrati 2008). Now also from northwestern Madagascar and the Mozambique Channel (new record). Propeamussium andamanicum is living on soft substrata of mud or muddy sand at bathyal and upper abyssal depths of - 281–2000 m (Dijkstra & Maestrati 2012). Present material live at - 1490–1750 m.

Remarks: The present specimens resemble in all morphological characters the type material, although the commarginal lirae on the left valve are slightly weaker. Descriptions of the soft parts and diet are given by Knudsen (1967: 274).