oscarps
The shell of the snail and the covers of the eggs are formed mainly by calcium carbonate like the shells of other molluscs. Because of this, they require a good amount of calcium in their diet and aqueous environment to produce a strong shell. A lack of calcium, or a fluctuation in the pH level in your environment, will probably make your shell thin, split, or have holes. Usually, a snail can repair its shell damage over time, if its living conditions improve, but some severe damage could be fatal to the snail. That is why snails develop better in limestone areas. Where calcium carbonate is scarce, some species are missing and others, the most adaptable, swallow calcium-containing stones, gnaw bones, limestone or calcium-rich plants.
