Shell ovate-trigonal to trigonal, moderately thin but strong, smooth to glossy, well inflated, posteriorly somewhat attenuate in large adults; umbones prosogyrate (more so in large adults) and raised; lunule heart-shaped, flat, weakly delineated by incised line; anterodorsal margin short, steeply sloping; narrowly convex terminally; ventral margin widely rounded; posterodorsal margin straight, steeply sloping, narrowly rounded at its extremity. Sculpture of growth striae supplemented by slightly raised ridges at anterior and posterior extremities. Colour externally white with heavy, black, ragged chevron patterns, lunule with prominent purple-black blotch; umbones white, lunule white with large brown-black blotch umbonally; shell internally white, sometimes with cream flesh colour centrally. Shell length to 38 mm.

Distribution and habitat
Western Indian Ocean to the West Pacific, in littoral muddy sand (not known from lagoonal or reef areas). Australia: Western Australia: One Arm Point, littoral sand, AMNH. 303274 (2pv); Broome, AMS C.141100 (lrv, llv); Buccaneer Archipelago, AMS C.42458 (many). Northern Territory: Vashon Head, Port Essingon, Coburg Peninsula, AMS C.93083 (2pv); Friday Island, Torres Strait. Queensland: AMS C.96956 (21v); Mapoon, AMS C.14238 (51v, lrv); Bowling Green Bay, Townsville, AMNH.303036 (lpv); trawled off Palm Island, AMNH.303315 (8pv); Dingo Beach, AMNH.303037 (lpv); Gloucester Passage, Dingo Beach, AMS C.72153 (4pv); Hayman Island, AMS C.97340 (2pv); Bustard Heads, Port Curtis, AMS C.141411 (lpv); Myora, Stradbrokc Island, AMNH.303373 (2pv). Thursday Island: Torres Strait, AMS C.141413 (lpv). Philippine Islands: (no localised data) QM MO. 14448 (in part) (lpv).

Remarks
The five pv from the Natural History Museum (BMNH.20000455) are labelled as 'syntypes'. Although these specimens were from the Cuming collection and the largest specimen has the word 'Type' glued to the shell, none matches either of Sowerby's (1851) illustrations of C. fastigiata (his figures 158, 159). There is no indication as to who originally gave the status of syntypes to the material in lot BMNH.20000455 (J. Pickering, personal communication). We have therefore decided to downgrade the status of this material from 'syntypes' to 'possible syntypes' and, in the absence of any definite type material. Sowerby's figure 159 closely resembles Lioconcha pseudofastigiata n. sp., based on the external coloration and the attenuate valve shape , but, in the absence of any illustration of the interior of the shell by Sowerby (or any matching specimen from the Natural History Museum collection), it is impossible to be absolutely certain of the identity of this specimen. Sowerby gives 'Sydney, Australia' as the locality for L. fastigiata, but if his figure 159 represents L. pseudofastigiata n. sp. (a species presently recorded only from the Philippine Islands), then it would seem highly likely that some, and possibly all, of his material was collected in the Philippine Islands. We know of no records of this species from Sydney or any locality south of Moreton Bay, southern Queensland.
The colouration of dark brown zigzag flammules over the valves and the dark brown blotch associated with the lunule, combined with the smooth, inflated shell appear to be constant within the species and help to distinguish it from other species of Lioconcha. Superficially L. fastigiata may be mistaken for L. castrensis (which also shows zigzag flammules), but that species always has a thick, rounded shell featuring a heavy hinge line (and teeth) and a strongly raised lunule. Specimens of L. fastigiata from the Philippine Islands differ from those from Australia in having more elongate, slightly thinner shells, which exhibit a diffuse brown band internally. The relationship between L. fastigiata and L. annettae seems to be a very close one, although the former is chiefly a coastal inhabitant, whereas the latter is always found in reef lagoonal localities. It is possible that L. annettae may prove to be a localised reef form of L. fastigiata, but until the relevant anatomical and/or molecular data become available to test this suggestion, we continue to recognise both as valid taxa. Certain forms of L. ornata (in the rather broad sense adopted herein) examined in the present study, especially material from New Caledonia, also suggest a relationship between this species, L. fastigiata and L. annettae. Again, this requires clarification based on non-conchological characters. Cernohorsky (1972) illustrates a fairly typical specimen of L. fastigiata from Caboni Beach, Fiji, and this represents the most easterly confirmed record of this species within the Pacific. Although Kira (1962) records L. fastigiata from Japanese waters ('the Amami Islands and southwards', p. 162) his illustrated specimen is clearly identifiable as L. ornata.