Parvamussium pauciliratum (E.A. Smith, 1903 )

Dijkstra, Henk H. & Beu, Alan G., 2018, Living Scallops of Australia and Adjacent Waters (Mollusca: Bivalvia: Pectinoidea: Propeamussiidae, Cyclochlamydidae and Pectinidae), Records of the Australian Museum (Rec. Aust. Mus.) 70 (2), pp. 113-330 : 137

Parvamussium pauciliratum (E.A. Smith, 1903)

Figs 8G,J, 9

Amussium paucilirata [sic] Smith, 1903: 622, pl. 36, figs 23–24.

Parvamussium pauciliratum (Smith) .–Dijkstra, 1991: 14, figs 33–34; Dijkstra, 1995b: 26, figs 107–110, 151–152; Dijkstra & Kastoro, 1997: 261, figs 73–74; Dijkstra, 1998a: 12, pl. 1, figs 1–2; Dijkstra & Maestrati, 2008: 92; Dijkstra & Moolenbeek, 2008: 16; Xu & Zhang, 2008: 78, fig. 215; Huber, 2010: 224; Dijkstra, 2011: 42, pl. 1016, figs 2, 3a–b, 4; Dijkstra, 2013: 19, pl. 3, figs 1–1d, pl. 4, fig. 9.

Type data. Lectotype (pr) designated by Dijkstra (1995b: 28) NHMUK 1903.9.17.17, 2 paralectotypes (pr) NHMUK 1903.9.17.18/1–2. Type locality: Maldive Islands , S Nilandu Atoll, alive, 2–66 m.

Comments on type data. Although the original registration number indicated 4 specimens, only 3 types are now present in NHMUK .

Figure 9. Distribution of Parvamussium multiliratum Dijkstra (circles), P. pauciliratum (Smith) (stars), P.retiolum Dijkstra (triangles) and P.scitulum (Smith) (squares).

Additional material examined. — AUSTRALIA: QUEENSLAND: NE of Cairns ,16°33'54"– 16°33' 48"S 146°09'42"– 146°09'36"E , dead, 55 m (3 v, C.157659; 2 v, C.157660, in part); SE of Swain Reefs , 22°31.4'S 152°32.6'E , dead, 100 m (3 v, C.157661,in part).— INDONESIA: Ceram, Piru Bay , 3°10'S 128°08'E,(2 v,C.338458) . — PAPUA NEW GUINEA: Port Moresby, Fairfax Harbour, 0.5 ml off Wharf , 9°26'S 147°06'E ,dead, 15–18 m (1 v,C.165515);off Port Moresby,W end of Manubada Island , 9°31'S 147°10'E , alive, 18–22 m (many v, C.165513); off Port Moresby, on sheltered NW side of Manubada Island , 9°31'S 147°10'E , dead, 23 m (many v,C.165514); Rabaul Harbour, Matupi Island , 4°14'S 152°12' E , dead, beach grit (1 v, C.338459).

Description. Shell fragile, small, up to c. 8 mm high, hyaline or opaque, sub-orbircular, inequivalve, right valve more convex than left, slightly inequilateral, auricles almost equal, umbonal angle c. 105°, prodissoconch c. 200 µm in height. Left valve creamy-white stained with white dots, right valve uniform white.

Left valve glossy, with a few minute growth lines, covered with microscopic granules. Auricles smooth on most specimens; a few have delicate commarginal lirae near anterior margin.

Right valve also glossy, smooth apart from microscopic granules. Anterior auricle with minute commarginal lirae. Dorsal margin straight. Internal riblets rudimentary, 1 or 2, with a small auricular lira on each side in most specimens. Resilifer triangular. Byssal notch very narrow.

Habitat. Living as shallow as 2 m in the littoral zone and on the continental shelf, free on soft sediment (sand and coral rubble, muddy sand or mud).

Distribution. Maldive Islands , 2–66 m ( Smith, 1903); Indonesia, 34–467 m (dead) (Dijkstra, 1991; Dijkstra & Kastoro, 1997); Philippines, 32–82 m (Dijkstra, 2011, 2013); Papua New Guinea, 48–125 m (Dijkstra, 1998a); Chesterfield Islands , Coral Sea, 150–225 m (dead); New Caledonia, 27–45 m (Dijkstra, 1995b); Solomon Islands , 509–522 m (Dijkstra & Maestrati, 2008). Present material taken alive from southern Papua New Guinea at 18– 22 m. Maximum depth range of live-taken specimens is 2– 522 m. Present material from Australia (Queensland) taken only dead at 55– 100 m.

Remarks. The present specimens are identical to the type specimens from the Maldive Islands (Indian Ocean).

Parvamussium pauciliratum is a new record forAustralia.