Large quantities of calcium carbonate crystals were present in the albumin gland of the reproductive system of the fresh-water snail Pomacea paludosa. X-ray diffraction analyses indicated that they were vaterite. Scanning electron microscope observation of the albumin gland revealed that they occurred as spherules and were distributed throughout the gland. Vaterite spherules were present in the albumin gland of Pomacea urceus and the capsule gland of Pila virens. The mineral portion of the egg capsules was also vaterite. The egg capsule of these snails consisted of two morphologically distinct layers. Vaterite is less common in nature than the other two polymorphs of calcium carbonate, calcite and aragonite, and has not been recorded in the reproductive system of molluscs. It is interesting to note that in these snails calcium carbonate was present as vaterite both in the storage organ and fully differentiated egg capsule.
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