ornamental articles. The most valuable mother-of-pearl is obtained from four species; Pinctada maxima P. margaritifera Trochus niloticus and Turbo marmoratus although a number of others ( Pinctada sp, Haliotis sp. and some freshwater mussels) are also used. The mother-of-pearl trade declined with the development of plastics, but recently it has been undergoing a revival; 3apan, Taiwan and South Korea are the centres of the carving industry. Currently there is an annual demand of about 6000 tonnes of unprocessed Trochus shell alone (13). The Philippines and Indonesia export large quantities of Pinctada sp, and Indonesia, the Solomon Islands and other Pacific islands export Trochus niloticus and Turbo marmoratus (14). In the South Pacific the export of mother-of-pearl may be the only source of cash income for people on some of the remoter islands (13) and the button industry is being revived in some areas (45). 3apan is the main producer of pearls, techniques for culturing these valuable molluscan products having been developed in this country first. It is thought that there is potential for pearl culture industries in other countries (18). Shell collecting has been a popular hobby for centuries. The ornamental shell trade is now a major industry, centred in the Philippines which exported about 3500 tonnes of ornamental shells in 1979. The main consumer is the U.S.A, whose imports rose from just over 1000 tonnes in 1969 to about 4400 tonnes in 1978. There are currently an estimated 1000 shell dealers in the U.S.A, and in Florida alone there are probably between 5000 and 10 000 retail outlets such as gift shops, hotels and department stores (33). Other major consumers are Japan and many European countries. The species most in demand are the big colourful gastropods from the Indo-pacif ic and Caribbean, such as the Queen Conch Strombus gigas the Tiger Cowry Cypraea tigris, the Pearly or Chambered Nautilus Nautilus pompilius and helmet shells, cones and volutes (33). The jewellery industry has made use of shells for many centuries. Naples in Italy has long been important for cameos, carved from the shell of the Indo-pacific gastropod Cassis Recently shell jewellery and other shellcraft articles have undergone a revival in popularity. Small cowries, dove shells and a variety of other shells are used in large quantities to make necklaces, lampshades, decorated boxes and figurines. The Philippines is the main supplier and is also the centre of the capiz shell (Placuna placenta ) industry. Nearly three and half million capiz shell articles were exported in 1979 (14). THREATS TO SURVIVAL As for many marine invertebrates there are few examples of molluscs that are threatened with extinction. The Giant Clams (see data sheet) are possible exceptions, but even they may still occur in large numbers on some of the remoter Pacific atolls. There are, however, many examples of commercially important species which have been locally over-exploited; some examples are given below. Less information is available on the effects of pollution and habitat disturbance, but in some cases these factors could have serious effects. 1. Exploitation Abalone has been overfished in many countries including Japan, China, South Africa, New Zealand, south Australia and Mexico (43). Haliotis tuberculatus has practically disappeared from the English Channel (16), and the Pacific species were heavily overfished on the coast of California, U.S.A. earlier this century (22). Oysters were once the food of poor people but are now considered a luxury in most countries. Natural oyster grounds have been destroyed through coastal development, domestic and industrial pollution, poor management and over-exploitation. In some cases, where pollution has not harmed the bivalves themselves, they have been rendered unfit for human consumption. By 1964, 12 per cent of the total active shellfish-producing area in the U.S.A. had been closed for health reasons and oyster production on the Atlantic coast had been reduced from 43 million kg in 1920 to less than half that amount. Oyster fisheries have also been lost in the Philippines, Australia, Great Britain and on the Pacific coast of the U.S.A. (21,39,40,43). Scallops were fished to virtual commercial extinction 71