Propeamussium investigatoris (E. A. Smith, 1906)
SMITH, E. A. 1906. Natural history notes from H.M. Indian Marine Survey Steamer “Investigator”, series 3 (10). On Mollusca from the Bay of Bengal and the Arabian Sea. The Annals and Magazine of Natural History [7th serie], 18: 157-175, 245-264 [p. 255]
1906 Amussium [sic] investigatoris E. A. Smith, 1906
1912 Amusium margaritiferum Dautzemberg & Bavay, 1912
1912 Amusium margaritiferum Dautzemberg & Bavay, 1912
Amussium [sic] margaritiferum nov. sp.; P. Dautzenberg & A. Bavay, 1912, Les lamellibranches de l'Expédition du Siboga, plate 27, figures 15-18.
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«Testa subcircularis, compressa, fragilis; valva dextra albido-pellucida, radiis opaco-albis circiter 10 picta, concentrice regulariter et tenuiter striata, intus costis ad 10 albis mediocriter crassis haud ad marginem attingentibus instructa; valva sinistra convexior, flavescens, radiis decem aurautiacis ornata, radiatim tenuiter costulata et concentrice delicate lamellata, lamellis supra costulas squamulatis, intus flavescens, costis albidis 10 tenuioribus munita; auriculae parvae, subaequales; umbones acuti, lateribus ad angulum circa 113° convergentibus.
Longit. 26 mm., alt. 26.5, diam. 5.5. Hab. Station 218, W. of Travancore, 224-284 fath., sand.
The sculpture of the two valves in this beautiful species is altogether different, that of the right valve, which is a little flatter than the left, consisting of very delicate and close-set regular lamellae or striae, whilst the left valve has numerous fine radiating riblets, which are minutely squamose through being crossed by the very fine concentric lamellae. The internal riblets, ten in number in each valve, do not reach to the margin, and those of the left valve are a little finer than those of the right. The colour of the valves is also different. The deeper valve is more or less orange-tinted within and without, whereas the light valve is almost white, with only a trace of colour on each side towards the dorsal slopes.» EDGAR ALBERT SMITH, 1906
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«Description. Shell up to 25 mm high, fragile, semi-translucent, oval to circular, inequivalve, equilateral, weakly inflated, left valve more convex than right, umbonal angle 100–110°. Prodissoconch c. 220 μm high. Left valve orange-tinted, right valve whitish.
Left valve sculptured with many unevenly spaced radial riblets, squamous in late growth stage. Latticed microsculpture only in early growth stage (up to c. 10 mm in height). Anterior and posterior auricles with 7–10 delicate squamous radial riblets, weaker on right valve. Right valve with fine, evenly spaced commarginal lamellae. Internal riblets 10 on most specimens, some with 2–4 intercostal rudimentary riblets near the margin and 2 auricular riblets. Dorsal margin straight. Resilifer triangular. Byssal notch and fasciole lacking. Dimensions. Illustrated specimen, Qld, E of GBR, 17°35'S 146°53'E, alive, 458–500 m (QM MO18021), 2 separate valves: rv: H 16.7, L 16.2; lv: H 18.7, L 16.4 mm; largest lv (incomplete ventral skirt; not illustrated): H 18.9, L 20.1 mm.
Habitat. Living in the bathyal zone, free on soft sediment (sand and mud).
Distribution. Northern Indian Ocean, 410–519 m (Smith, 1906); Indonesian Archipelago, 176–466 m (Dijkstra & Kastoro, 1997); Coral Sea, New Caledonia and Loyalty Islands, 600–960 m [as Propeamussium maorium] (Dijkstra, 1995b, 2001); Norfolk Island and Kermadec Islands, 512–549 m [as Propeamussium maorium] (Dijkstra & Marshall, 1997); Vanuatu, 602–650 m (Dijkstra, 2001); New Zealand, as far south as the Bay of Plenty (off Plate I., 37°30'S 176°48'E), 292–621 m, living at 337–585 m (Dijkstra & Marshall, 2008: 2, fig. 1); Solomon Islands, 367–500 m; Fiji, 395–699 m and Tonga: 395–710 m (Dijkstra & Maestrati, 2008). Present material from Australia living at 458–500 m.
Remarks. The present specimens from Australia differ slightly from the type material in having somewhat finer radial sculpture on the left valve, in lacking the latticed microsculpture in early ontogeny, and by the more whitish colour of the left valve (type material orange-tinted). We are grateful to Gary Rosenberg for pointing out that the name investigatoris is the genetive form of the noun “investigator” and is not declinable.
For comparison with Propeamussium jeffreysii (Smith, 1885) see Dijkstra & Kastoro (1997: 250). Propeamussium investigatoris is a new record for Australia.» DIJKSTRA, H. H. & A. G. BEU. 2018. Living scallops of Australia and adjacent waters (Mollusca: Bivalvia: Pectinoidea: Propeamussiidae, Cyclochlamydidae and Pectinidae). Records of the Australian Museum, 70 (2): 113-330, figs. 1-102. [p. 125]
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Propeamussium investigatoris (Smith); H. H. Dijkstra & A. G. Beu, 2018, Living scallops of australia and adjacent waters, figures 1A, 1E, 1K-1M.
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