Parvamussium multiliratum Dijkstra, 1995

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 : 135-137

Parvamussium multiliratum Dijkstra, 1995

Figs 8D,F, 9

Parvamussium multiliratum Dijkstra, 1995b: 26 : figs 31–34, 91–92; Dijkstra, 2001: 83; Dijkstra & Maestrati, 2008: 91; Dijkstra & Maestrati, 2010: 339.

Type data. Holotype (pr) MNHN Moll 21173, 16 paratypes (13 MNHN Moll21174–21181, 1 AM C.201711, 1 ZMA Moll.395024, 1 USNM886343). Type locality: Southern New Caledonia, 22°10'S 167°33'E, alive, 2100–2110 m (BIOCAL stn CP 72).

Additional material examined. — AUSTRALIA: QUEENSLAND: off Cairns, 16°02'– 16°0'S 147°14.9'– 147°13'E, dead, 1372 m (1 v, C.165480); off Cairns, 16°37' 42"S 146°20'24"– 146°18'42"E, dead, 658–685 m (1 v, C.374663); E of Lady Elliott Island, 24°0'S 153°06.5'E, dead, 476–531 m (3 v, C.165509); NE of Sandy Cape, 24°28.2'S 153°31.2'E, dead, 1330–1380 m (1 v, C.157674); E of Sandy Cape, 24°43.5' – 24°08'S 153°33.4'– 153°33.3' E, dead, 604 m (5 v, C.157675 [in part]). — SOLOMON ISLANDS : The Slot, 7°34.75'S 157°11.84'E, alive, 670–890 m (1 pr, C.157581). CORAL SEA: 11°31.09'S 145°22.31'E, alive, 1517–1611 m (many, C.165222); 11°35.61'S 145°29.42'E, alive, 1770–1863 m (4 pr, C.165220 [in part]); 11°40.98'S 145°36.85'E, alive, 2039–2052 m (2 pr, C.165221 [in part]); 11°56.72'S Figure 8. A, B, H, I, L, Parvamussium maorium Dell , separate valves, AM C.165528, MT Sprightly stn S73-2051, off Cape Naturaliste, TAS, 40°50.6'S 148°46.5'E, 399 m; rv anterior auricle exterior (A), rv exterior (B), rv interior (H), lv anterior auricle exterior (I), lv exterior (L). C, E, K, Parvamussium retiolum Dijkstra , lv only, AM C.165535, HMAS Kimbla sta. 1, E of Lady Elliott Island, QLD, 24°0'S 153°06'E, 476–531 m; lv anterior auricle exterior (C), lv exterior (E), lv interior (K). D, F, Parvamussium multiliratum Dijkstra , rv only, AM C.374663, HMAS Kimbla sta. C.22, off Cairns, QLD, 16°37'42"S 146°20'24"– 146°18'42"E, 658–685 m; rv exterior (D), rv anterior auricle exterior (F). G, J, Parvamussium pauciliratum (Smith) , rv only, AM C.157659, HMAS Kimbla stn C.10, NE of Cairns, QLD, 16°33'54"– 16°33'48"S 146°09'42"– 146°09'36"E, 55 m; rv anterior auricle exterior (G), rv exterior (J). Scale bars represent 1 mm (A, C), 4 mm (B, E, H, K, L), 2 mm (D, J), 0.5 mm (F, G, I).

145°48.39' E, alive, 2510–2523 m (1 pr, C.165219). TASMAN SEA: Lord Howe Rise , 27°13.36'S 160°43.41' E, alive, 1989 m (2 pr, C.165412); Lord Howe Rise , 27°58.99' S 162°51.55'E, alive, 1250 m (3 pr, C.165409).

Description. Shell up to c. 9 mm high, fragile, circular, inequivalve, hyaline, whitish, left valve slightly more convex than right valve, auricles subequal, umbonal angle about 110°. Prodissoconch c. 220 µm in height.

Both valves with 14 internal riblets plus 2 rudimentary interstitial ones, one auricular riblet on each auricle. External sculpture clearly visible from interior.

Left valve sculptured with widely spaced commarginal lamellae commencing at 3 mm shell height and extending to ventral margin. Unevenly spaced, delicate radial riblets developed near ventral margin, a few commencing earlier. Umbonal region glossy with a few white spots, otherwise translucent and dull due to microscopic granules. Auricles with commarginal lamellate riblets, more closely spaced near lateral margins than elsewhere.

Right valve with evenly arranged commarginal lirae, somewhat interrupted near ventral margin region by a disturbance of growth. Auricles with commarginal lamellae, more prominent on anterior auricle and more closely spaced on posterior. Dorsal margin straight, with a few scales, more prominent on anterior auricle. Byssal fasciole small, byssal notch present.

Habitat. Living in the bathyal and abyssal zones, free on soft sediment (muddy sand or mud).

Distribution. New Caledonia, 2100–2110 m, and Loyalty Islands , 1615–2040 m; Wallis and Futuna Islands , 400–765 m (dead); Vanuatu, 748–775 m (Dijkstra, 1995b, 2001). Living records from the Coral Sea (1517–2523 m), Solomon Islands (670–890 m) and Tasman Sea (1250–1989 m); Fiji, 640–687 m; Tonga, 360–436 m (dead) (Dijkstra & Maestrati, 2008); Austral Islands , 600–620 m (Dijkstra & Maestrati, 2010). Maximum depth range of live-taken specimens is 600–2523 m. Present specimens from Australia (Queensland) are deadtaken only, at 476–1380 m.

Remarks. The present specimens are morphologically identical to the type specimens from New Caledonia.

Parvamussium multiliratum is a new record forAustralia.