Propeamussium richeri Dijkstra, 2001
DIJKSTRA, H. H. 2001. Bathyal Pectinoidea (Bivalvia: Propeamussiidae,Entoliidae and Pectinidae) from Wallis and Fortuna Islands, Vanuatu Archipelago and New Caledonia.. In P. Bouchet & B. A. Marshall (Eds.), Tropical Deep-Sea Benthos, Volume 22, Mémoires du Muséum National d'Histoire Naturelle 185: 73-95. [p. 80, figs. 13-16]
2001 Propeamussium richeri Dijkstra, 2001
H. H. Dijkstra, 2001, figures 9-16.
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«TYPE MATERIAL. — Holotype (alive), MNHN. Paratypes: 45 MNHN, 2 AMS C203709-10, 2 HD 7100, 2 NMNZ M272625, 2 NSMT·Mo 71295-6, 2 USNM.
TYPE LOCALITY. — Eastern New Caledonia, channel SE of Ngoe, 21°45' S, 166°36' E, 250 m, [BATHUS 1. Sta. CP713].
MATERIAL EXAMINED. — New Caledonia. BATHUS 1: sta. CP669, 20°57' S, 165°35' E, 255·280 m, 1 lv, 1 rv (2 paratypes). — Sta. CP702, 20°55' S, 165°34' E, 591-660 m, 1 lv, 1 rv (2 paratypes). — Sta. DW706, 21°42' S, 166°34' E, 247-252 m, 3 lv, 3 rv (6 paratypes). — Sta. CP713, 21°45' S, 166°36' E, 250 m, 3 spms, 23 Iv, 19 rv (holotype (Figs 13-16) and 44 paratypes: 2 AMS, 2 HD, 34 MNHN, 2 NSMT, 2 USNM).
HALIPRO 1: sta. CP851, 21°43' S, 166°37' E, 314-364 m, 1 spm (paratype). DISTRIBUTION. — New Caledonia, 250-591 m, taken alive at 250-314 m.
DESCRIPTION. — Shell fragile, suborbicular, inequivalve, slightly inequilateral, up to ca 13 mm high, left valve somewhat more convex than right. Auricles unequal in size and texture, relatively small.
Prodissoconch ca 220 μm in height. Left valve sculptured with weak, irregularly spaced, small antimarginal lirae, commencing ca 1-1.5 mm below the angle top, multiplying and extending to ventral margin. Very weak commarginal growth lines developing in early ontogeny. Minute, closely spaced, commarginal lirae on shell disc, strongest near posterior margin. Anterior auricle with fine, closely spaced, commarginal lirae, somewhat lamellate near anterior margin; posterior auricle with identical though weaker sculpture. Antero- and posterodorsal margins with fine spines. Hinge line straight. Transparent, with light orange patches and numerous small white dots. Right valve sculptured with regular commarginal lirae, closely spaced in early growth stages, becoming wider towards periphery, and granular interstitial microsculpture. Anterior auricle with a small, radial, fasciolar ridge, and fine commarginal lamellae, stronger near disc. Antero- and posterodorsal margins serrate. Hinge line somewhat raised to the anterior and posterior margins. Orange, auricles whitish, internal ribs translucent white. Internal ribs generally 9, with 2 anterior auricular riblets and one posterior, commencing ca 2 mm below resilifer, extending to submarginal area. Resilifer triangular, somewhat oblong. Auricular crura rather broad. Byssal notch small, no ctenolium. Dimensions of the holotype: H 12.9 mm, L 12.1 mm, D 2.3 mm. REMARKS. — A closely similar species is Propeamussium rubrotinctum (Oyama, 1951), known from bathyal depths off southern Japan and New Caledonia, which differs from P. richeri in attaining larger size (up to ca 20 mm high, instead of ca 13 mm high), and in having a smooth and glossy Ieft valve disc with minute commarginal lamellae near the ventral margin and one or two delicate radial plicae near the posterior margin (P. richeri is sculptured with numerous antimarginal lirae and minute, closely spaced, commarginal lirae), in having weaker commarginal lirae on the right valve. P. rubrotinctum differs further in lacking a fasciolar ridge on the anterior auricle of the right valve, in having typically 10 internal ribs instead of typically 9 and in colouration (P. rubrotinctum is less colourful with larger white dots, especially from New Caledonia).
Propeamussium maorium (Dell, 1956), from New Zealand, is also a closely similar species, which differs in having a reticulate or commarginal sculpture near the ventral margin of the left valve (P. richeri has antimarginal sculpture or is smooth), in having the auricles of the right valve more prominently sculptured, with internal ribs generally 10, and in being less colourful (lacking maculations) or opaque whitish (P. richeri is more brightly orange coloured with white maculations, and more transparent). ETYMOLOGY. — The specific epithet is named after Dr Bertrand RICHER DE FORGES (ORSTOM, Nouméa), manager of several New Caledonian marine expeditions.»
HENK H. DIJKSTRA, 2001
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