Chlamydella Iredale, 1929

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 : 158-159

Chlamydella Iredale, 1929

Chlamydella Iredale, 1929: 164 , 188. Type species (by original designation): Cyclopecten favus Hedley, 1902 ; Recent , off New South Wales, Australia, 75–91 m.

Diagnosis. Shell inequivalve, minute, up to c. 3 mm high, circular to posteriorly oblique; prodissoconch weakly inflated; left valve sculptured with radial and/or commarginal riblets or striae or smooth, right valve with commarginally elongate hexagonal (honeycomb-like) microstructure (simple calcitic prismatic outer layer); auricles unequal; byssal notch well-developed; no ctenolium; no internal lirae.

Figure 23. A, D, Chlamydella favus (Hedley) , rv only, AM C.269876, same sample as Fig. 21C, F, K; rv exterior (A), prodissoconch of specimen in Fig. 23A (D). B, E, G, Hyalopecten ponderi sp. nov., holotype, pair, AM C.209770, ORV Franklin stn 15, Coral Sea, 11°40.98'S 145°36.85'E, 2039–2052 m; rv exterior (B), lv exterior (E), rv anterior auricle exterior (G).C, F, H–J, Cyclochlamys nepeanensis (Pritchard & Gatliff) , separate valves, AM C.165517, in sample with Chlamydella favus (Hedley) (AM C.269876, specimens in Fig. 21C, F–L), Euston Reef, off Cairns, SW side of reef, 16°41'S 146°15'E, 21 m; rv exterior (C); prodissoconch of specimen in Fig. 23C (F), lv exteriors (H, J), prodissoconch of specimen in Fig. 23J (I). Scale bars represent 0.5 mm (A, G, H), 2 mm (B), 1 mm (C, J), 200 µm (D), 3 m (E), 100 µm (F, I).

Distribution. Pleistocene–Recent. Australia, New Zealand, Japan, sublittoral to bathyal. Cyclopecten (Chlamydella) sp. from the early Miocene (Aquitanian) Bhuban Formation, NE India (Mazumder & Tiwari 2012: 31, pl. 1, fig. 8) is based on an unidentifiable mould. This is the only published fossil record we are aware of, although D. Jablonski (pers. comm. 27 Jun 2017) reported an unpublished Pleistocene record from Henderson Island.

Discussion. Hayami & Kase (1993: 61) enumerated representative species of Chlamydella from Australia, subantarctic seas and Japan. They also suggested that Cyclochlamys might be a senior synonym of Chlamydella .Although they placed both newly described species, i.e. Chlamydella incubata Hayami & Kase, 1993 and Chlamydella tenuissima Hayami & Kase, 1993 in the present genus, the figured prodissoconchs of the two species differ strongly (Hayami & Kase, 1993, fig. 204, lv prodissoconch of C. incubata conical, typical of Cyclochlamys ; figs 215–216, lv prodissoconch of C. tenuissima weakly inflated, typical of Chlamydella ). Dijkstra & Marshall (2008: 22) synonymized the two genera, but Dijkstra & Maestrati (2012: 394) differentiated them, based mainly on their distinct prodissoconchs, and placed both genera in family Cyclochlamydidae .