This very large, thick-shelled bivalve is ovate to almost circular in outline. Insides the valves are purplish, the exterior purplish with a thick black to olive periostracum. Most have well developed concentric growth lirae on the exterior surface particularly anteriorly. The hinge teeth heterodont, very strong, with up to three cardinal teeth in each valve which may be bifid. The well-developed lateral teeth are coarsely serrated. There is a strong external ligament posterior to the umbones. There is no lunule and no escutcheon. The pallial line is entire.
The gills are eulamellibranch and the foot is a compressed, tongue shaped foot lacking a byssal groove. There are two relatively short posterior siphons and short papillae on the mantle edge. The mantle margins are not fused ventrally.
Batissa (Batissa) violacea (Lamarck, 1818)
Original name: Cyrena violacea Lamarck,1818. Lamarck, J. B. P. (1818). Histoire Naturelle des Animaux sans Vertèbres. Paris: Deterville & Verdiere, 5:1-612.
Type locality: Unknown.
Lives in lower freshwater sections of rivers and at freshwater-estuarine interface. In intertidal to shallow water, infaunal, burrowing in sand and mud. In part pedal feeders. Dioecious, non-brooding (oviparous) with free swimming larvae.
Tropical northern Australia. On old record from the Richmond River in northern New South Wales needs confirmation. Also in Andaman Islands, Taiwan, Malaysia, Thailand, Indonesia, Philippines, Papua New Guineas and some SW Pacific Islands (eg. Fiji, New Caledonia).
Huber (2015) lists Batissa australis Deshayes, 1855 from Australia. This is not followed here.
Beesley, P. L., Ross, G. J. B. & Wells, A., Eds. (1998). Mollusca: The Southern Synthesis. Parts A & B. Melbourne, CSIRO Publishing.
Huber, M., Langleit, A. & Kreipl, K. (2015). Compendium of Bivalves 2. A Full-Color Guide to the Remaining Seven Families. A Systematic Listing of 8,500 Bivalve Species and 10,500 Synonyms. Hackenheim, Germany, ConchBooks.
Lamprell, K. & Healy, J. (1998). Bivalves of Australia, volume 2. Leiden, Backhuys Publishers.