a bivalve marine mollusc with anacreous interior, much admired in Tasmania and used forpendants and necklaces, Trigonia margaritacea, Lamarck,of the order Pectinaceae. It is the largest trigonia occurring in Australasia, and the only onefound in Tasmania. Numerous extinct species are characteristicof the Mesozoic rocks. The only living species existing areconfined to Australia.