Samples are wet-sieved through nested oversize (18 inch) custom-made geological sieves. There are three mesh sizes: 2 mm, 1 mm, and 0.5 mm. I use oversize sieves because I work with large samples (generally 15-20 liters) in order to get specimen counts that are large enough for quantitative analysis. In Britain, where the climate is wet and snails are abundant, researchers can routinely work with only 1-2 kilograms of sediment.