Diagnosis
Shell robust but not thick, elongate-ovate, glossy, moderately inflated; anterior margin rounded; posterior margin rounded, becoming slighty attenuate and truncate in large adults, ventral margin rounded; umbones markedly prosogyrate, more so in adults; lunule heart-shaped, flat, well delineated by incised line. Sculpture of fine growth striae dominated by many coarse, concentric raised ridges developed as rounded ribs; interstices approximately equal in width to ribs. Colour externally flesh to light brown, with several rays of darker brown and sometimes underlying broad zigzags; lunule and dorsal margin purple-brown; shell internally white with mauve-brown staining subumbonally (staining dominating in small juveniles). Shell length to 27.7 mm.

Distribution and habitat
Indo-West Pacific, in sand and rubble, to 115 m. Material examined
Lectotype. Cytherea philippinarum Hanley, 1844, H. Harvey Coll., ex Hanley, designated by Lamprell and Kilburn (19996): 45, BMNH.1912.6.18.20.
Paralectotypes. BMNH.1966346/1-7; Callista amirantium lectotype designated by Lamprell and Kilburn (199%) three paralectotypes from same lot, BMNH.1910.3.17.14.17.
Other material examined. Australia: Murray Island, Torres Strait, AMS C.36345 (1 pv); Arafura Sea, 115 m, AMS C.358022 (lrv); Lindeman Island, AMS C.358023 (llv). Papua New Guinea: (cx P. Pecker, no localised data), AMNH.303252 (4pv). New Britain: Duke of York Island, AMS C.68244 (in part) (lpv). Philippine Islands: AMS C.34910 (2pv). New Caledonia: Baie de St Vincent (Lagon: stn 186) (llv) Scctcur de Canala (Lagon: stn 703) (lpv) 40 m; Grand Recif Mcngalia (Lagon: stn 839) (2pv, llv) 37 m; (stn 849) (lpv, llv, lrv) 41 m; Scctcur des Bclep (Lagon: stn 1213) (lpv, lrv) 32 m (MNHN, ORSTOM Expeditions). Andaman Island: AMS C.34486 (3pv). Reunion: Cap la Houssaye (llv) 8-17 m, 1984, NM K.4548 (llv); Saint Paul Bay; 3-30 m, J. Drivas, NM K.2780 (3pv, 141v, 14rv). Mauritius: Off Black R., 24-30 m, NM K.7547 (lpv).

This is a very distinctive species that is easily differentiated from other heavily ridged Lioconcha by a combination of a glossy, flesh to light brown shell (featuring darker brown rays) and a comparatively large adult size. Habe (1951) used this species as the type of his subgenus Sulcilioconcha but, as discussed later in the present account, his defining features are inadequate. Habe's reference to a 'purplish' shell appears to apply more so to the inside colouration of the valves rather than the overall external colouration (excepting the lunule area). However, we have not examined Japanese material of L. philippinarum and it is possible that geographic variation in external colouration may occur in this species. Although not mentioned by Lamprell and Kilburn (1999b), the lectotype of L. philippinarum (selected by them) also shows broad, fine zigzag markings. In most specimens examined herein, only faint traces of zigzags could be discerned, largely due to the predominance of brown rays in the colour pattern. On external appearance, L. philippinarum is possibly more likely to be confused with certain other heavily ridged venerids, such as various Callista species, but these taxa all have a deep, well-developed pallial sinus. The closest relatives to L. philippinarum within the genus Lioconcha appear to be L. gordoni and L. dautzenbergi, which, likewise, have glossy shells and exhibit a well delineated lunule tinged with purple-brown (however, in L. gordoni, colour is limited to the periphery of the lunule). These species differ from each other in external colour patterns and degree of rib development, irrespective of the size of the individual. In addition, neither L. gordoni nor L. dautzenbergi reaches the maximum size attained by L. philippinarum. Lioconcha trimaculata also exhibits a purple-brown lunule, but has a decidedly non-glossy surface and a tendency to show slight sinuation of the posteroventral margin. Lamprell and Kilburn (1999/)) have recently confirmed Deshayes* (1863) record of this species from Reunion in their survey of venerids from the South African and Mozambiquan region. Lamprell and Kilburn (1999/)) also note that all specimens from the syntype series of C. amirantium are paler than typical Philippine Islands shells, but agree in all other characters.