Small, L to 11 mm, subcircular, posteriorly slightly truncate in juveniles, shallow posterior sulcus, moderately inflated. Shell colour white, internally often yellowish. Sculpture of fine, low commarginal lamellae crossed by low radial ribs which are broader and more prominent towards the anterior and posterior. Radial ribs are slightly fluted where crossed by commarginal lamellae. Lunule elongate, lanceolate, slightly asymmetrical. Ligament internal, short, situated on a broadly triangular resilifer. Hinge: right valve with single, narrow, cardinal tooth, anterior and posterior lateral teeth small; left valve with two narrow cardinal teeth, small anterior lateral and posterior lateral teeth. Anterior adductor muscle scar medium length, detached for ca. 50 % of length. Posterior scar ovate. Pallial line entire, irregularly lobate. Shell margin finely crenulate, with crenulations coarser towards anterior and posterior.

Rugalucina munda is closely similar in shell morphology to R. vietnami¬ca and R. angela and we previously confounded the species (Glover and Taylor 2001). In shell morphology the differences are subtle; R. munda is more ovoid, the radial ribs are finer, and the inner shell margin is less coarsely crenulated compared to R. angela and R. vietnamica. Furthermore, Glover and Taylor (2001: fig. 16) recorded a distributional gap between Australian and Asian records of P. vietnamica. Features of the anatomy and ctenidial bacteria of R. munda from Port Douglas, Qld were described by Glover and Taylor (2001, as Pillucina vietnamica).

Type locality. Moreton Bay, Queensland, Australia.
Material examined. Australia: Western Australia: Parry Harbour, Kimberley (WAM). Broome Bay (WAM). Northern Territory: Darwin, East Point. Gove (NMV), Groote Eylandt G. of Carpentaria (AMS). Friday Island, Torres Strait (AMS). Queensland: Somerset, Cape York (AMS), Port Douglas (16°28'48"S, l45°27'4l"E) seaward edge of mangroves (NHMUK). Buchan Point, Cairns (AMS), Port Denison, Bowen (AMS), Seaforth, Mackay (AMS), Yeppoon (AMS), Tin Can Bay, Snapper Point (25°54T2.18"S, 153°00'58"E), mangroves, muddy sand. Moreton Bay, Redland Bay (27°37'03"S, 153°19'06"E), muddy seagrass, 1 m. North Stradbroke Island, near Dunwich, seagrass (27°29'44"S, 153°23'57"E).
Distribution. Northern and north eastern Australia.
Habitat. Intertidal and shallow subtidal muddy sand, nearshore seagrass and man¬grove fringe.

Hedley (1913: 267) recommended that the name Lucina munda be rejected as unrecognisable because at that time type material had not been identified and the original description ambiguous. Later, because the incorrect type material had been isolated in the NHMUK collection the name Lucina munda had been regarded (e.g., Lamprell and Whitehead 1992) as a synonym of Ctena bella (Conrad, 1837). More recent recognition of the original type material (JDT & EAG) showed that Lucina (Codakia) munda (syntypes figured here for the first time from the Cuming collection and collected in Moreton Bay by Mr Strange) is a species similar to Rugalucina vietnamica and R. angela. In his description Adams (1856) highlights the dichotomously radiating ribs and the radially grooved inner shell margin and the yellowish shell interior. Rugalucina munda is thus the earliest name for the Australian species.