Anisus septemgyratus
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Anisus septemgyratus is a species of air-breathing freshwater snail, an aquatic pulmonate gastropod mollusk in the family Planorbidae, the ram's horn snails.
Whorl (mollusc)
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A whorl is a single, complete 360° revolution or turn in the spiral or whorled growth of a mollusc shell. A spiral configuration is found in the shells of numerous gastropods, and in shelled cephalopo
Counting gastropod whorls. In this example a shell with 3¾ whorls is shown, with the fourth whorl expanding more rapidly than whorls 1–3.
A fossil shell of the marine gastropod Turritella communis. This shell has nine whorls
The shell of the marine gastropod Haliotis asinina has fewer than two whorls