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Twenty-five species of Pectinoidea (24 Propeamussiidae, 1 Cyclochlamydidae) are herein listed from the Mozambique Channel, northwestern and southern Madagascar, and northeastern South Africa. New species: Propeamussium rosadoi, Parvamussium catillus, Parvamussium kilburni, Parvamussium puillandrei, Parvamussium strongae, Cyclopecten cassiculus, Cyclopecten kantori, Cyclochlamys bacachorda. New synonym: Amussium sewelli Knudsen, 1967 = Propeamussium watsoni (E.A. Smith, 1885). New records for the Mozambique Channel and northwestern Madagascar: Propeamussium andamanicum, Propeamussium arabicum, Propeamussium caducum, Propeamussium jeffreysii, Propeamussium sibogai, Propeamussium watsoni, Parvamussium formosum, Parvamussium scitulum, Parvamussium torresi, Parvamussium vesiculatum, Cyclopecten kapalae, Similipecten eous. New records for southern Madagascar: Propeamussium jeffreysii, Propeamussium sibogai, Propeamussium watsoni, Parvamussium formosum, Parvamussium scitulum, Parvamussium thyrideum, Par...

Cyclopecten cancellus Dijkstra, 1991 Figs 15H–I,K, 16 Cyclopecten cancellus Dijkstra, 1991: 21, figs 66–70; Dijkstra, 2001: 90, figs 33–35; Dijkstra & Moolenbeek, 2008: 18; Dijkstra & Maestrati, 2008: 97; Dijkstra & Maestrati, 2013b: 474. Type data. Holotype (lv) RMNH56560, 14 paratypes (v) RMNH56561–56566. Type locality: Indonesia, Flores Sea, off SW Salayer, 6°22.4'S 120°26.3'E, dead, 130–155 m (SNELLIUS-II stn 4.153). Additional material examined. — AUSTRALIA: QUEENSLAND: off Cairns, 16°36'12"– 16°35'54"S 146°15'24"– 146°14'18"E, dead, 110–201 m (1 v, C.165464). WESTERNAUSTRALIA: S of Cowaramup Bay, near mouth of Margaret River, 33°57'S 114°59'E, dead (2 v, C.165468); Kilcarnup, N side of Margaret River, 33°57'S 114°59'E, dead, beach (1 v, C.374666); Ellensbrook, 33°55'S 115°0'E, dead, beach (2 v, WAM S12952); Cowaramup, 33°52'S 115°0'E, dead (2 v [rudimentary internal riblets], WAM S12559; 1 v, WAM S12535); Rottnest Island, 32°0'S 115°30'E, dead, beach (9 v, WAM415.91); Rottnest Island, Bathurst Point, 32°0'S 115°30'E, dead, beach (1 v, WAM414.91); Rottnest Island, Ricey Beach, 32°0'S 115°30'E, dead, beach (3 v, WAM413.91; 1 v, C.165465); Cottesloe, Cable Station, 33°0'S 115°45'E, dead (1 v, WAM481.91); NW of Beagle Island, 29°43'S 114°17'E, dead, 274–283 m (1 v, C.165466). — NEW CALEDONIA: off New Caledonia, 20°16'S 169°51'E, alive, 85–100 m (2 pr, C.165234). Figure 16. Distribution of Cyclopecten cancellus Dijkstra (circles), C. horridus Dijkstra (star), C. powelli Dell (triangle) and C. reticulatus sp. nov. (squares). Description. Shell small, up to c. 3 mm high, convex, subcircular, opaque, whitish to cream, wider than high, inequivalve, almost equilateral, left valve slightly more convex than right, auricles almost equal in size, umbonal angle c. 100°. Left valve with coarse reticulate sculpture with scaly intersections, radial riblets (c. 10) more prominent than commarginal lamellae, both widely spaced, commencing at 0.5 mm shell height and increasing in prominence ventrally, with secondary interstitial radial riblets. Auricles with 1–2 radial riblets crossed by prominent commarginal lamellae. Right valve with closely spaced commarginal lamellae. Anterior auricle with 2–4 weak radial riblets, posterior smooth. Dorsal margin straight. Byssal notch moderately deep, byssal fasciole narrow. Habitat. Living in the sublittoral and bathyal zones amongst rubble on soft bottoms. Distribution. Indonesia, 130–375 m, dead; Vanuatu, 140–175 m, dead (Dijkstra, 1991, 2001); Fiji, 500–614 m, dead (Dijkstra & Maestrati, 2008). Now also from New Caledonia (85–100 m) and Australia (beach drift and 110–283 m, dead). Remarks. The present species is similar to the type specimens from Indonesia, although some specimens from Western Australia have some rudimentary internal riblets, which are lacking in typical specimens. Cyclopecten cancellus is a new record for Australia (empty shells only)., Published as part of Dijkstra, Henk H. & Beu, Alan G., 2018, Living Scallops of Australia and Adjacent Waters (Mollusca: Bivalvia: Pectinoidea: Propeamussiidae, Cyclochlamydidae and Pectinidae), pp. 113-330 in Records of the Australian Museum (Rec. Aust. Mus.) (Rec. Aust. Mus.) 70 (2) on page 149, DOI: 10.3853/j.2201-4349.70.2018.1670, http://zenodo.org/record/5299017

Genus Cyclopecten Verrill, 1897 Cyclopecten Verrill, 1897: 70. TYPE SPECIES (SD, by Sykes et al. 1898). — Pecten pustulosus Verrill, 1873 (Recent, off Newfoundland, Canada)., Published as part of Dijkstra, Henk H. & Maestrati, Philippe, 2017, New species and new records of littoral and bathyal living Pectinoidea (Bivalvia: Propeamussiidae, Cyclochlamydidae, Pectinidae) from the western and southwestern Pacific, pp. 473-485 in Zoosystema 39 (4) on page 477, DOI: 10.5252/z2017n4a3, http://zenodo.org/record/4578634, {"references":["SYKES E. R., SMITH E. A. & CRICK G. C. 1898. - Mollusca. The Zoological Record 34 (7): 1 - 78."]}

Cyclopecten hoskynsi (Forbes, 1844) Fig. 5 h���l Pecten hoskynsi Forbes, 1844 (p. 192). Amussium hoskynsi Forbes���Jeffreys 1879 (p. 562). Propeamussium (Cyclopecten) hoskynsi hoskynsi (Forbes, 1846) ��� Nordsieck 1969 (p. 46, pl. 7, fig. 30.15). Propeamussium hoskynsi (Forbes) ��� Di Geronimo & Panetta 1973 (p. 99, pl. 3, fig. 13); Di Geronimo & Li Gioi 1980 (pl. 3, figs. 1���2). Cyclopecten hoskynsi (Forbes, 1846) ��� Poppe & Goto 1993 (p. 71, pl. 10, fig. 9). Cyclopecten hoskynsi (Forbes, 1844) ��� Giannuzzi-Savelli et al. 2001 (p. 172, fig. 324); Repetto et al. 2005 (p. 300, bottom left fig); Oliver et al. 2016 (online resource). Cyclopecten hoskynsi (Forbes) ���Rosso et al. 2010 (fig. 10 E). Diagnostic characters. Flattened, subrounded shell; moderately long right anterior auricle with 7���8 radial ribs and deep byssal notch; subequal left auricles with concentric lamellae; right valve with crowded concentric cordlets and about 15 inner radial ribs sometimes restricted to the peripheral area; left valve with sparse radial rows of moon-shaped, recurved lamellar nodes. Prodissoconch: shell type ST-2D; length about 150 ��m; roundish D-shaped outline; low convex profile; P-1 surface pitted; P-2 replaced by narrow metamorphic lip; transition to the nepioconch well marked. Occurrence. Box-corer samples BC04 (5 specimens), BC05 (7), BC41 (1), BC66 (12), BC67 (9), BC71 (27), BC72 (146); cores BC04 (1), BC05 (5), BC21 (11), BC51 (8), BC52 (1), BC67 (1), BC72 (17). Maximum height: 6 mm. Distribution and habitat. The species is distributed all along the western margin of the Atlantic (from Greenland to Cape Verde) and in the Mediterranean, where it thrives on soft sediments from shelf edge to bathyal depths (Nordsieck 1969; Oliver et al. 2016). It was regarded as a typical element of VP (bathyal mud) biocoenosis (Di Geronimo et al. 1982). In the Santa Maria di Leuca CWC biotope, it was regarded as abundant in mollusk mud, and common in coral rubble and Gryphus-Isidella thanatofacies (Rosso et al. 2010). Fossil record. Pliocene of Sicily (Monterosato 1872); bathyal Pleistocene of central and southern Italy (Di Geronimo & Li Gioi 1980; Di Geronimo & Bellagamba 1985; Barrier et al. 1987; Di Geronimo & La Perna 1997; Di Geronimo et al. 2005)., Published as part of Negri, Mauro Pietro & Corselli, Cesare, 2016, Bathyal Mollusca from the cold-water coral biotope of Santa Maria di Leuca (Apulian margin, southern Italy), pp. 1-97 in Zootaxa 4186 (1) on page 28, DOI: 10.11646/zootaxa.4186.1.1, http://zenodo.org/record/165288, {"references":["Forbes, E. (1844) Report on the Mollusca and Radiata of the Aegean Sea, and on their distribution, considered as bearing on Geology. Reports of the Thirteenth Meeting of the British Association for the Advancement of Science; held at Cork in August 1843, 130 - 193.","Nordsieck, F. (1969) Die europaischen Meeresmuscheln (Bivalvia) vom Eismeer bis Kapverden, Mittelmeer und Schwarzes Meer. Gustav Fischer Verlag, Stuttgart, XIII + 256 pp.","Di Geronimo, I. & Panetta, P. (1973) La Malacofauna Batiale del Golfo di Taranto. Conchiglie, 9 (5 - 6), 69 - 121.","Di Geronimo, I. & Li Gioi, R. (1980) La malacofauna Wurmiana della Staz. BS 77 / 4 al largo di Capo Coda Cavallo (Sardegna Nord orientale). Annali dell'Universita di Ferrara (Nuova Serie), section IX, 6 (supplement), 155 - 190.","Poppe, G. T. & Goto, Y. (1993) European Seashells. Volume II. (Scaphopoda, Bivalvia, Cephalopoda). Verlag Christa Hemmen, Wiesbaden, 221 pp.","Giannuzzi-Savelli, R., Pusateri, F., Palmeri, A., Ebreo, C. †, Coppini, M., Margelli, A., Bogi, C. (2001) Atlante delle conchiglie marine del Mediterraneo. Vol. 7 (Bivalvia: Protobranchia-Pteriomorphia). Evolver, Roma, 246 pp.","Repetto, G., Orlando, F. & Arduino, G. (2005) Conchiglie del Mediterraneo: 1770 specie illustrate con distribuzione e frequenza. Amici del Museo \" Federico Eusebio \", Alba, 392 pp.","Oliver, P. G., Holmes, A. M., Killeen, I. J. & Turner, J. A. (2016) Marine Bivalve Shells of the British Isles (Mollusca: Bivalvia). Amgueddfa Cymru-National Museum Wales. Available from: http: // naturalhistory. museumwales. ac. uk / britishbivalves. (Accessed 25 August 2016)","Di Geronimo, I., Li Gioi, R. & Sciacca, V. (1982) La fauna Pleistocenica dell'abbeveratoio Conzo (Grammichele, Catania). Geologica Romana, 21, 577 - 601.","Monterosato, T. A. di (1872) Notizie intorno alle conchiglie fossili di Monte Pellegrino e Ficarazzi. Ufficio Tipografico Michele Amenta, Palermo, 44 pp. http: // dx. doi. org / 10.5962 / bhl. title. 50743","Di Geronimo, I. & Bellagamba, M. (1985) Malacofaune dei dragaggi BS 77 - 1 e BS 77 - 2 (Sardegna nord orientale). Bollettino della Societa Paleontologica Italiana, 24 (2 - 3), 111 - 129.","Barrier, P., Casale, V., Costa, B., Di Geronimo, I., Olivieri, O. & Rosso, A. (1987) La sezione Plio-Pleistocenica di Pavigliana (Reggio Calabria). Bollettino della Societa Paleontologica Italiana, 25 (2), 107 - 144.","Di Geronimo, I., Messina, C., Rosso, A., Sanfilippo, R., Sciuto, F. & Vertino, A. (2005) Enhanced biodiversity in the deep: Early Pleistocene coral communities from Southern Italy. In: Freiwald, A. & Murray Roberts, J. (Eds), Cold-water Corals and Ecosystems, Springer, Berlin, pp. 61 - 86. http: // dx. doi. org / 10.1007 / 3 - 540 - 27673 - 4 _ 4"]}

Cyclopecten kantori sp. n. Fig. 7A–G Etymology:After Dr Yuri I. Kantor, leading researcher of the Department of Invertebrate Morphology at the A.N. Severtzov Institute of Ecology and Evolution, Russian Academy of Sciences in Moscow. Participant of several French expeditions. Description: Shell up to 11.9 mm in height, fragile, subcircular, inequivalve, almost equilateral, left valve more inflated than right valve (nearlY flat), auricles dissimilar in shape, anterior auricle larger than posterior one, umbonal angle 120°, internal ribs lacking, semi-translucent whitish. Prodissoconch 220 µm long. Left valve reticulately sculptured throughout shell disc by narrow radial riblets and overrunning commarginal lirae with delicate solide nodules on intersections. On central part of disc c. 10 radial riblets per mm, c. 7–8 commarginal lirae. Reticular sculpture commences in early growth stage, radial riblets enlarge gradually in ontogeny by intercostal riblets towards the ventral margin. Commarginal lirae more prominent than radial riblets, very closely spaced in early growth stage, gradually wider in later ontogeny. Auricular sculpture similar to that of shell disc with stronger solid nodules on the intersections. Right valve sculptured with commarginal lirae, closely spaced (c. 30 per mm) near umbonal area, coarser and wider on central part of disc (c. 8 per mm). Posterior auricle continuous with shell disc, sculptured with fine close-set commarginal lirae, anterior auricle and byssal fasciole seperated from shell disc by sharply incised groove, sculptured with prominent commarginal lirae and 8 crowded radial riblets with nodular intersections. Byssal notch moderately deep, byssal fasciole narrow. Dimensions: Holotype: Height 11.9 mm, width 11.1 mm, convexity 3.2 mm. Type material: Holotype, pr (MNHN IM-2007-38440). Type locality: NW MADAGASCAR: In front of Narendry Bay (14°30'S 47°27'E), - 274–325 m, live, campaign Miriky, stn CP3241, 06.vii.2009. Distribution and habitat: So far northwestern Madagascar, living bathyally on soft substrata at - 274– 325 m. Remarks: The morphologically closest congeneric species is the abyssally (- 2928– 2930 m) living similar sized Cyclopecten textus Dijkstra & Marshall, 2008, recorded from the Lord Howe Rise. This species could be distinguished from C. kantori by the following characters: by shell shape (C. textus is almost circular, C. kantori somewhat higher than wide), by shape of auricles (C. textus has smaller auricles (c. 2 mm) measured between end of hinge and disc, C. kantori somewhat broader (2.5 mm)), by commarginal sculpture of the left valve (C. textus has less commarginal sculpture in early ontogeny, P. kantori more close-set), and by reticulate sculpture in the central part of the disc of left valve (C. textus more squarely, C. kantori more elongate). A somewhat similar reticulated sculptured bathyally living species is Parvamussium retiolum Dijkstra, 1995, recorded from the southwestern Pacific. This species could be easily distinguished from C. kantori by its more oblique elongate shape (C. kantori sub-circular), and by its well-developed internal ribs (lacking in C. kantori)., Published as part of Dijkstra, H. H. & Maestrati, P., 2015, Pectinoidea (Bivalvia: Propeamussiidae and Cyclochlamydidae) from the southwestern Indian Ocean, pp. 585 in African Invertebrates 56 (3) on pages 618-619, DOI: 10.5733/afin.056.0307, http://zenodo.org/record/7914533

Cyclopecten cassiculus sp. n. Fig. 6A–G Etymology: From the Latin cassiculus (m.) (small spider’s web), after the sculpture of left valve that resembles a spider’s web with fine raindrops on the intersections. Description: Shell up to 8.9 mm in height, fragile, lv opaque, rv semi-transparent, somewhat higher than wide, inequivalve, flattened and somewhat rough, left valve slightlY more convex than right valve, inequilateral, anterior auricle larger than posterior, umbonal angle 90°–95°, colour of left valve creamy, right valve whitish. Prodissoch 170 µm long. Left valve sculptured with very closely spaced commarginal lirae in early growth stage (c. 10 per mm), more prominent and widely spaced on central shell disc (c. 4–5 per mm), 8–10 fine radial lirae commence c. 0.8–1.0 mm below umbo, increasing to c. 15 strong primary lirae near periphery with interstitial secondary lirae, intersections with small nodules on primary radial lirae in early growth stage, more lamellar in adult stage, small nodules on secondary interstitial riblets, similar sculptured auricles almost continuous with shell disc. Right valve with very weak, regularly spaced, delicate commarginal lamellae (c. 10 per mm). Anterior auricle with 6–7 antimarginal noduliferous lirae, posterior auricle continuous with disc with verY fine and close-set commarginal lirae. Byssal notch moderately deep, byssal fasciole rather small, no ctenolium. Hinge line straight. Resilifer triangular. Internal ribs lacking. Dimensions (holotype): height 8.9 mm, width 8.0 mm, convexity 2.9 mm. Type material: Holotype, pr (MNHN IM-2007-41951), paratype, pr (MNHN IM-2007-41954).Type locality: MADAGASCAR: Near Mahajamba Bay (14°50'S 46°57'E), - 340–446 m, live, campaign Miriky, stn CP3248, RV Miriky, leg. P. Bouchet & Y. Kantor, 07.vii.2009. Paratype: MADAGASCAR: Between Majunga and Cap Saint-André (15°32'S 45°45'E), - 327–730 m, live, campaign Miriky, stn CP3265, RV Miriky, leg. P. Bouchet & Y. Kantor, 10.vii.2009. Distribution and habitat: NW Madagascar, living upper bathyally at - 327–340 m (minimum depth range). Remarks: The closest resembling species is Parvamussium cassium Dijkstra, 1991, recorded from deep water (- 450–600 m) off Indonesia. Cyclopecten cassiculus morphologically differs from P. cassium bY having prominent radial and fine commarginal lirae (in P. cassium weaker and more equal of prominence), in having secondary intercostal radial lirae in late ontogeny (P. cassium in earlier growth stage), in having fine interstitial radial lirae, up to 6 near ventral margin (one radial lira in P. cassium), and in having coarser nodules and lamellae on intersections of lirae (P. cassium very small nodules). Both species are lacking internal ribs, although P. cassium has a short auricular riblet (very weak in the present species). A somewhat resembling species is Parvamussium vidalense (Barnard, 1964), recorded from eastern South Africa and herein also from southern Madagascar. This species has a reticular sculpture on the left valve of more closelY spaced, finer radial and commarginal lirae with short spines or curved lamellae on the radial and commarginal intersections. Moreover, several rudimentary interior ribs are present (lacking in C. cassiculus)., Published as part of Dijkstra, H. H. & Maestrati, P., 2015, Pectinoidea (Bivalvia: Propeamussiidae and Cyclochlamydidae) from the southwestern Indian Ocean, pp. 585 in African Invertebrates 56 (3) on pages 616-617, DOI: 10.5733/afin.056.0307, http://zenodo.org/record/7914533, {"references":["BARNARD, K. H. 1964. Contributions to the knowledge of South African marine Mollusca. Part 5. Lamellibranchiata. Annals of the South African Museum 47: 361 - 593."]}

Cyclopecten kapalae Dijkstra, 1990 Cyclopecten kapalae Dijkstra, 1990: 29, figs 1-5. MATERIAL EXAMINED. — Australia. New South Wales, off Sydney, 914- 907 m, holotype spm (AMS C.155831.1). Vanuatu. SANTO 2006, stn AT19, 15°40.8’S, 167°00.5’E, 503-600 m, 6 lv, 4 rv. — Stn DB69, 15°24.4’S, 167°13.0’E, 38 m, 1 spm. DISTRIBUTION. — Eastern Australia, Solomon Islands, Vanuatu (new record) and Kermadec Islands. Earlier known from 512-549 m (Dijkstra & Maestrati 2008: 97), the Santo specimen live collected in 38 m shows that this is a shallow offshore species., Published as part of Dijkstra, Henk H. & Maestrati, Philippe, 2012, Pectinoidea (Mollusca, Bivalvia, Propeamussiidae, Cyclochlamydidae n. fam., Entoliidae and Pectinidae) from the Vanuatu Archipelago, pp. 389-408 in Zoosystema 34 (2) on page 393, DOI: 10.5252/z2012n2a12, http://zenodo.org/record/5165513, {"references":["DIJKSTRA H. H. 1990. - A new species of scallop from off New South Wales, Australia (Bivalvia: Propeamussiidae). Journal of the Malacological Society of Australia 11: 29 - 32.","DIJKSTRA H. H. & MAESTRATI P. 2008. - New species and new records of deep-water Pectinoidea (Bivalvia: Propeamussiidae, Entoliidae and Pectinidae) from the South Pacific, in HEROS V., COWIE R. H. & BOUCHET P. (eds), Tropical deep-sea benthos, volume 25. Memoires du Museum national d'Histoire naturelle 196: 77 - 113."]}

Cyclopecten ambiguus n. sp. (Fig. 2 K-P) Cyclopecten cancellus – Tröndlé & Boutet 2009: 6 [listed from Austral Is as C. cancellus]. TYPE MATERIAL. — Rapa. Atelier RAPA stn 43, 27°36.8’S, 144°18.3’W, 45 m, holotype lv (MNHN 21385).— Same data, paratypes, 3 lv, 4 rv (4 MNHN 21386, 2 ZMA Moll. 4.09.011, 1 NMNZ M.287778). TYPE LOCALITY. — Austral Islands, Rapa Island, Baie de Haurei, 27°36.8’S, 144°18.3’W, 45 m (Atelier RAPA, stn 43). ETYMOLOGY. — From the transforming sculpture (commarginal in juvenile stage, reticular in adult stage) on the left valve (Latin ambiguus, adjective meaning changeable, variable or inconstant). OTHER MATERIAL EXAMINED. — Rapa. Atelier RAPA, stn 30, 27°38.2’S, 144°18.2’W, 16-20 m, 7 lv, 2 rv. — Stn 44, 27°36.3’S, 144°18.2’W, 30 m, 4 lv. — Stn 47, 27°36.7’S, 144°19.1’W, 33 m, 1 rv. — Stn 48, 27°34.1’S, 144°22.1’W, 36 m, 5 lv, 3 rv (1 ZMA). Banc Arago. BENTHAUS, stn DW 1979, 23°22’S, 150°44’W, 176-340 m, 1 lv. DISTRIBUTION. — Austral Islands, only single valves at 16-176 m depth. DESCRIPTION Shell up to c. 4 mm high, circular, inequivalve, equilateral, left valve slightly more inflated than right valve (nearly flat), auricles nearly equal in size, unequal in shape, opaque whitish (lv), translucent (rv). Left valve disc sculpture commencing immediately by very closely spaced commarginal lirae (c. 20 per mm) to 1 mm from the top margin, followed by a reticulate sculpture of widely spaced radial lirae (12 or 13) and overrunning commarginal lirae (c. 5 per mm), forming weak nodules on the intersections. Secondary intercalated radial lirae commence on the central part of the disc. Anterior and posterior auricle with 4 or 5 strongly developed commarginal lirae and one weak radial lira. Right valve disc with very closely spaced commarginal lirae in early growth stage, gradually slightly wider to the ventral margin. Auricles with strong commarginal lirae (numerous on anterior, 9 or 10 on posterior).Hinge line straight. Byssal notch relatively deep, byssal fasciole rather broad. Internal rudimentary riblets near ventral area in adult stage. Dimensions of holotype: H 3.0 mm, W 3.0 mm. REMARKS The present species is morphologically closest (similar size, shape and reticulated sculpture) to Cyclopecten cancellus Dijkstra, 1991, from the southwestern Pacific (and was indeed listed from the Australs by Tröndlé & Boutet as C. cancellus), but differs in having very closely spaced lirae in early growth stage (c. 20 per mm in C. ambiguus, vs c. 6 or 7 in C. cancellus), a weaker sculpture of radial lirae, lacking radial sculpture on the auricles (C. cancellus 2 or 3), and rudimentary inner riblets (usually lacking in typical C. cancellus). Cyclopecten thyrideus (Melvill, 1907), from the northwestern Indian Ocean is also close to C. ambiguus (somewhat similar in size, shape, sculpture and internal rudimenrary riblets), but differs in having a fine microscopic radial sculpture in early growth stage immediately below the dissoconch stage (a commarginal sculpture in C. ambiguus), weaker commarginal lirae on the left valve and fewer commarginal lirae on the anterior auricle of the right valve). Cyclopecten ryukyuensis Hayami & Kase, 1993, from southern Japan and the Philippines is similar in size, shape and sculpture, but differs in having widely spaced commarginal lirae and irregular antimarginal intercalated scratches (see Hayami & Kase 1993: figs 195, 197) in early growth stage on the left valve (only closely spaced commarginal lirae in C. ambiguus), fewer intermediate secondary radial lirae, and in lacking internal rudimentary riblets. Finally, Cyclopecten secundus (Finlay, 1926), from New Zealand, also has a somewhat similar sculpture in early growth stage as C. ryukyuensis, although with more closely spaced (but much wider and stronger than in C. ambiguus), more prominent commarginal lirae with strong lamellae on the intersections (almost lacking in C. ambiguus) and sometimes 1 or 2 internal rudimentary riblets near the periphery (usually and more numerous in C. ambiguus)., Published as part of Dijkstra, Henk H. & Maestrati, Philippe, 2010, Pectinoidea (Mollusca, Bivalvia, Propeamussiidae, Entoliidae and Pectinidae) from the Austral Islands (French Polynesia), pp. 333-358 in Zoosystema 32 (2) on pages 340-341, DOI: 10.5252/z2010n2a6, http://zenodo.org/record/4521132, {"references":["TRONDLE J. & BOUTET M. 2009. - Inventory of marine molluscs of French Polynesia. Atoll Research Bulletin 570: 1 - 87.","DIJKSTRA H. H. 1991. - A contribution to the knowledge of the pectinacean Mollusca (Bivalvia: Propeamussiidae, Entoliidae, Pectinidae) from the Indonesian Archipelago. Zoologische Verhandelingen 271: 1 - 57.","MELVILL J. C. & STANDEN R. 1907. - The Mollusca of the Persian Gulf, Gulf of Oman and Arabian Sea as evidenced mainly through the collections of Mr F. W. Townsend, 1893 - 1906, with descriptions of new species. Part 2. Pelecypoda. Proceedings of the Zoological Society of London 1906: 783 - 848.","HAYAMI I. & KASE T. 1993. - Submarine cave Bivalvia from the Ryukyu Islands: systematics and evolutionary significance. The University Museum, The University of Tokyo, Bulletin 35: i-vi, 1 - 133."]}

Cyclopecten cancellus Dijkstra, 1991 Cyclopecten cancellus Dijkstra, 1991: 21, figs 66-70. MATERIAL EXAMINED. — Indonesia. Off SW Salayer, 130-155 m, holotype lv (RMNH 56560). Vanuatu. SANTO 2006, stn ZB06, 15°36.8’S, 167°01.3’E, 30 m, 1 spm. — Stn EP10, 15°34.5’- 38.0’S, 167°05.1’-13.6’E, 45-101 m, 1 spm. — Stn NB12, 15°33.1’S, 167°09.6’E, 20 m, 1 spm, 3 lv, 1 rv. — Stn AT14, 15°23.7’-24.0’S, 167°12.9’-13.5’E, 102-120 m, 1 lv, 1 rv. — Stn EP19, 15°37.5’-38.0’S, 167°05.1’-05.6’E, 80-94 m, 2 lv.— Stn DB20, 15°30.5’S, 167°01.4’E, 22-25 m, 1 spm. — Stn EP21, 15°37.7’S, 167°05.2’E, 99 m, 1 spm. — Stn ZS22, 15°33.1’S, 167°09.6’E, 27-29 m, 1 lv. — Stn EP36, 15°33.1’- 33.3’S, 167°12.4’-12.7’E, 20-60 m, 1 spm. — Stn EP40, 15°33.1’-33.6’S, 167°16.4’-16.5’E, 125-156 m, 1 spm. — Stn FB43, 15°28.4’S, 167°14.9’E, 19 m, 1 lv, 2 rv. — Stn FP50, 15°36.8’S, 167°08.7’E, 25 m, 1 spm. — Stn DB63, 15°26.9’S, 167°15.8’E, 21 m, 1 rv. — Stn DB77, 15°27.9’S, 167°14.7’E, 42-45 m, 1 spm. — Stn FS77, 15°33.1’S, 167°09.6’E, 29 m, 3 lv, 2 rv. — Stn DB80, 15°37.1’S, 167°07.5’E, 18 m, 1 lv. — Stn DS99, 15°32.5’S, 167°16.9’E, 100-105 m, 1 spm, 3 lv, 1 rv. — Stn DS102, 15°34.1’S, 167°16.0’E, 98-100 m, 1 spm, 2 lv, 1 rv. — Stn DS103, 15°34.1’S, 167°16.0’E, 70-80 m, 3 lv, 2 rv. — Stn DS105, 15°33.0’S, 167°16.7’E, 92 m, 3 lv. DISTRIBUTION. — Indonesia, Vanuatu and Fiji. Bathymetric range: earlier known from shells in 130-614 m; Santo specimens collected alive in 20-125 m. REMARKS The Santo specimens are indistinguishable from the type material. The rudimentary internal riblets are very variable, i.e. lacking (typically) one or several short rudimentary., Published as part of Dijkstra, Henk H. & Maestrati, Philippe, 2012, Pectinoidea (Mollusca, Bivalvia, Propeamussiidae, Cyclochlamydidae n. fam., Entoliidae and Pectinidae) from the Vanuatu Archipelago, pp. 389-408 in Zoosystema 34 (2) on page 393, DOI: 10.5252/z2012n2a12, http://zenodo.org/record/5165513, {"references":["DIJKSTRA H. H. 1991. - A contribution to the knowledge of the pectinacean Mollusca (Bivalvia: Propeamussiidae, Entoliidae, Pectinidae) from the Indonesian Archipelago. Zoologische Verhandelingen 271: 1 - 57."]}

Cyclopecten bavayi Dijkstra, 1990 Figs 32, 33 Cyclopecten (Cyclopecten) bavayi Dijkstra, 1990a: 5, fig. 9. MATERIAL EXAMINED. — Solomon Islands. SALOMON 1: stn CP 1781, 08°31’S, 160°38’E, 1036-1138 m, 1 spm (Figs 32, 33). DISTRIBUTION. — Indonesia, shells in 835 m (Dijkstra 1990a: 5). New record for the Solomon Islands. Present specimen live in 1036-1138 m. REMARKS. — The present specimen from the Solomons is nearly indistinguishable from the type material, although the commarginal and intercalated radial sculpture of the left valve are slightly more widely placed in the present specimen. Other morphological characters are extremely similar., Published as part of Dijkstra, Henk H. & Maestrati, Philippe, 2008, New species and new records of deep-water Pectinoidea (Bivalvia: Propeamussiidae, Entoliidae and Pectinidae) from the South Pacific, pp. 77-114 in Mémoires du Muséum national d'Histoire naturelle 196 on page 97, {"references":["DIJKSTRA H. H. 1990 a. - Three new pectinacean species from the Indonesian Kermadec Islands. Molluscan Research 18: 73 - 114."]}

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