الفهرس 
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Abstract
There are about 40,000 described secies of living gastropods in the worhd (Brusca and Brusca, 1990), or about three-quarters of the p[-hylum Mollusca. Molluscs have a mantle, which is a fold of the dorsal body wall that creates a mantle cavity. The mantle cavity usually houses the ctenidia, anus and ores of the nephridial and reproductive systems. just under the mantle epithelium there are shell glands responsible for biomineralisatation and shell formation.