Notochlamys hexactes ( Lamarck, 1819 )

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 : 249-251

Notochlamys hexactes ( Lamarck, 1819)

Figs 72A,E–G, 73, 74A–D

Pecten hexactes [Péron] in Lamarck, 1819: 178, no. 59; Deshayes, 1836: 154, no. 59; Dijkstra, 1994: 492, pl. 30, figs 130–131 [holotype].

Pecten undulatus G. B. Sowerby II, 1842: 60 , pl. 19, figs 206–207; Reeve, 1852: sp. 73, pl. 20, fig. 73; Smith, 1885: 299; Tate & May, 1901: 441; Bavay, 1905b: 22, 27; Hedley, 1916a: 157; Thiele, 1930: 591 (junior primary homonym of Pecten undulatus Nilsson, 1827 ).

Pecten tasmanicus A. Adams & Angas, 1863: 428 , pl. 37, figs 21a–b; Smith, 1885: 299; Bavay, 1905b: 27.

Pecten mariae Tenison Woods, 1876: 158 ; 1878a: 33.

Chlamys undulatus [sic] (Sowerby).–Pritchard & Gatliff, 1904a: 263; Iredale, 1924: 194.

Chlamys anguineus [sic] Finlay, 1927: 527 (replacement name for Pecten undulatus Sowerby, 1842 ).

Notochlamys anguineus [sic] (Finlay).–Cotton, 1930: 233; Cotton & Godfrey, 1938: 94, fig. 80; Macpherson & Chapple, 1951: 145; Cotton, 1961: 98, fig. 83.

Notochlamys tasmanica (A. Adams & Angas) .–Cotton & Godfrey, 1938: 95, fig. 81; Waller, 1991: 30, pl. 3, figs 11–12; Rombouts, 1991: 48, pl. 18, fig. 1; Richmond, 1992: 85, fig. 122.

Notochlamys anguinea (Finlay) .–Iredale & McMichael, 1962: 11; Rombouts, 1991: 47, pl. 16, figs 7–7c.

Mesopeplum tasmanicum (A.Adams & Angas) .–Macpherson & Gabriel, 1962: 305, fig. 347; Lamprell & Whitehead, 1992: [32], pl. 14, fig. 81.

Decopecten [sic] anguineus (Finlay) .–Coleman, 1975: 89, fig. 266.

Semipallium (Mesopeplum) anguineus [sic] (Finlay).– Dijkstra, (1983–1989) 1983: 3, figs.

Mesopeplum anguineum (Finlay) ; Lamprell & Whitehead, 1992: [30], pl. 13, fig. 80.

Notochlamys hexactes (Lamarck) ; Beu & Darragh, 2001: 65, figs 17A–G; Raines & Poppe, 2006: 220, 221, pl. 169, figs 1–7; Huber, 2010: 206.

Type data. Pecten hexactes Lamarck : holotype (rv) MNHN Moll21196. Type locality: “Habite les mers de la Nouvelle Hollande, au port du Roi Georges” [ Western Australia , Albany, King George Harbour].

Pecten undulatus Sowerby : syntypes (1 pr + 2 lv + 1 rv) NHMUK [not registered]. Type locality: “Mediterranean?”. This locality is incorrect, herein designated as Tasmania [this locality is written on the board of the type specimens].

Pecten tasmanicus A. Adams & Angas : holotype (pr) NHMUK 1950.5.23.1. Type locality: Tasmania, Oyster Bay.

Pecten mariae Tenison Woods : holotype (lv) TMH5749 . Type locality: Tasmania, east coast.

Comments on type data. See Dijkstra (1994: 492) and Beu & Darragh (2001: 66).

Figure 73. Distribution of Notochlamys hexactes (Lamarck) (circles) and Pascahinnites coruscans coruscans (Hinds) (stars).

Additional material examined. — AUSTRALIA: NEW SOUTH WALES: Twofold Bay , 37°05.13'S 149°55.35'E, dead (1 v, C.049885) . VICTORIA: off Lakes Entrance, 38°03'S 148°03.5' E,dead, 36–46 m (9 v, C.132129;1 v,C.375060) ; netween Cape Howe & Lakes Entrance, 38°13'S 149°06'E, dead, 146–158 m (3 v, C.096256);Torquay, 38°21'S 144°18'E,dead (6 v, C.097550);off Wilsons Promontory, 39°10'S 146°23'E, alive, 54 m (2 pr, C.097549). TASMANIA: Black River Beach, near Stanley, 40°51'S 145°18'E, dead (3 v, C.097501) ; 41°09'S 146°10'E, alive (2 pr, C.119739); Swansea, 42°08' S 148°04'E, alive (1 pr, C.017687); Port Arthur , 43°09'S 147°51'E, alive, 15 m (4 v, C.097502) ; Cox Bight, 43°30'S 146°15'E, dead (1 v, C.375084). SOUTH AUSTRALIA: 50 ml SE of Kangaroo Island , 37°0'S 138°33'E, dead, 77 m (12 v, C.375083) ; Largs North Beach , c. 19 km N of Adelaide, 34°49'S 138°29'E, dead (1 v, C.375086) ; Nuyts Archipelago, N of St Francis Island , 32°29'S 133°18'E, dead, 20–30 m (4 v, C.375087) ; St Vincents Gulf, 35°0'S 138°0'E, dead (4 v, C.001422) ;Neptune Islands , 35°17'S 136°05'E,dead, 73 m (4 v,C.019244). WESTERN AUSTRALIA: GreatAustralian Bight,c. 50 km SSW of St Francis Island ,33°0'– 33°05'S 133°05'– 133°10' E, dead, 64 m (1 v, C.375085) ; Great Australian Bight, 50 ml SW of Cape Adieu , 32°42'S 131°27'E, dead, 79 m (1 v, C.375082) ; Recherche Archipelago, Cape Le Grand & New Island , 34°01' S 122°07.5' E, dead, 26–33 m (1 v, C.300344) ; Esperance, between Sandy Hook Island & Cape Le Grand , 34°02'S 122°0' E, alive, 31–35 m (1 pr, WAM) ; Esperance , 33°51'S 122°53'E, alive (1 pr, WAM) ; Esperance , 33°51'S 122°53'E, jetty, dead, 10 m (1 v, WAM) ; Esperance area , 33°52'S 121°54'E, dead (2 v, C.375081) ; Great Australian Bight, E of Hood Point , 34°21'S 121°16'E, dead, 82 m (5 v, C.300343) ; Bremer Bay , beach between John Cove and James Cove, 34°24'S 119°25'E, dead, beach (1 v, WAM) ; E of Cheyne Bay , 34°55'S 119°0' E, dead, 71–76 m (6 v, C.375080) ; E of Albany, Cheyne Beach , approx. 34°36'E 118°46'E, dead (1 v, WAM) ; Oyster Harbour via Albany, Emu Point , 35°0'S 117°57'E, dead, 9 m (1 v, WAM) ;King George Sound, 35°03'S 117°58'E, dead (1 v, C.043570; 1 pr, C.375079); S of Cape Leeuwin ,34°25'– 34°45'S 114°40'– 115°0'E, dead, 73–144 m (2 v,C.102077) ; Cape Naturaliste, Eagle Bay , 33°33'S 115°04'E, dead, 9 m (1 pr, WAM) ;Dunsborough, 33°36'S 115°06'E, alive, 0–3.6 m (1 pr + 2 v, C.101042); NW of Bunbury , 32°57.05'S 114°48'E, dead, 122–139 m (3 v, WAM) ; Warnboro Sound , 32°16.15' S 115°39.09'E, dead, 17 m (2 v, WAM) ; Cockburn Sound , 32°16.04'S 115°38.09'E, dead, 20–22 m (3 v, WAM) ; Fremantle, Cockburn Sound,off Woodmans Point , 32°12' S 115°44'E,dead(2 v, WAM; 1 v, WAM) ;Perth, Cottosloe Beach, 31°59'S 115°45' E, dead (1 v, C.010573; 14 v, C.075259; 7 v, C.097551; 1 v, C.103825; 3 v, C.130898; 3 v, C.130899); Perth, off Cottesloe , 31°59'S 115°45'E, dead (11 v, WAM) ; W of Swanbourne , 31°58.42'S 115°39.07'E, dead, 18.3 m (1 v, WAM) ; Perth, City Beach, 31°56'S 115°45'E, dead (1 v, C.069272); W of Dongara , 29°11'S 114°26' E, dead, 49.9 m (5 v, WAM) ; 80 km W of Dongara , 29°07.06'S 114°04.08'E, dead, 64 m (1 v, WAM) ; NW of Rottnest Island , 32°01'S 115°30'E,dead, 146 m (1 v, WAM) ; NW of Bluff Point , 27°40' S 113°03' E,dead, 128 m (1 v, WAM) ; NW of Cape Naturaliste , 23°40'S 114°28'E,dead, 137 m (1 v, WAM) .

Description. Shell up to 67 mm high (Huber, 2010), most specimens under 40 mm; solid, weakly and almost equally inflated, subcircular, slightly wider than high, inequivalve, almost equilateral, auricles unequal, umbonal angle c. 110–115°; colour variable, white, yellow, orange, red, purple, brown to almost black; some specimens uniformly coloured or with paler blotches, or dark radial streaks between radial riblets.

Both valves sculptured with 5–11 plicae, weaker towards anterior and posterior ends of disc, prominent and relatively narrow with wide interspaces on left valve, weaker and with

Figure 74. A–D, Notochlamys hexactes (Lamarck) , specimens in Fig. 72A, E–G; lv exteriors (A, C), rv exteriors (B, D). E, F, Pascahinnites coruscans coruscans (Hinds) , specimen in Fig. 72H, I; rv exterior (E), lv exterior (F). G–I, Pedum spondyloideum (Gmelin) , 2 valves in AM C.041556, beach, Lizard Island, QLD; (G, I) immature rv, exterior (G), interior (I); (H) specimen in Fig. 72D, lv exterior. Scale bars represent 20 mm (A–D), 10 mm (E, F), 30 mm (G–I).

narrower interspaces on right valve, with numerous radial riblets on plicae and in interstices (Tasmanian morph), riblets very weak or almost lacking (typical morph), covered with shagreen microsculpture throughout.Anterior auricles larger and longer than posterior ones, with 6–9 prominent radial costae; riblets much weaker and fewer on posterior auricles. Byssal notch moderately deep, byssal fasciole rather narrow. Functional ctenolium with c. 6 teeth in most specimens,

lacking in some adults. Internal costae with weakly carinate edges in a narrow zone just inside ventral margin.

Dimensions. Illustrated specimens: tasmanica form, Tasmania, ex J. C. Cox collection (AM C.119739): rv: H 40.8, L 41.6 mm; lv: H 40.7, L 41.8 mm; D 9.7 mm; anguinea form, WA, King George Sound (AM C.375079): rv: H 32.2, L 31.9 mm; lv: H 31.8, L 31.9 mm; D 11.8 mm.

Habitat. In Western Australia living in the littoral zone, free amongst the roots of sea grass, where currents have exposed the roots in gullies. Usually requires calmer, almost estuarine conditions. In Tasmania amongst shell rubble on soft sediment (sand and/or mud).

Distribution. Southern Western Australia (from W of Dongara, 29°07.06'S), South Australia, Victoria, Tasmania to southernmost New South Wales (Twofold Bay). Present specimens alive in the intertidal zone to 54 m.

Remarks. Notochlamys hexactes inhabits only the temperate waters of southern Australia and is extremely variable in shape (left valve flat and right valve weakly convex to equally inflated and pyxoid), sculpture (arrangement, number and prominence of primary radial plicae and secondary radial ribs) and colour (typically highly variable and brightly coloured, Tasmanian morph usually only purple). The “western” (typical or anguinea morph) and “eastern” populations ( tasmanica morph) intergrade completely and are not distinguishable geographical forms (see also Beu & Darragh, 2001: 66). As noted above under Equichlamys bifrons , Notochlamys hexactes has lecithotropic development, and the great range of variation presumably results from the poor exchange of genes between distant populations.