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| Phylum Mollusca |
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 Free living aquatic forms (freshwater or marine), some amphibious. |
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 Body is soft and unsegmented enclosed in a glandular mantle covered by usually a shell. |
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 Coelom is reduced to a pericardial cavity around the heart. |
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 Digestive system is complete. |
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 Respiratory organs are in the form of gills called ctenidia. |
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 Locomotor structure is represented by muscular foot. |
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 They have soft-body, which is differentiated into three regions - head, visceral hump and foot. |
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 Visceral hump is covered by a thin, fleshy fold called mantle. |
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 Mantle secretes a calcarious shell, which may be external or internal. |
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 Reproduction is sexual. Either unisexual or bisexual, development is direct. |
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| fig.10.18 - Examples of Mollusca |
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| The phylum is divided into six classes |
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| fig. 10.19 - Snail Anatomy |
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