Shell thickness in the land snail Theba pisana (Pulmonata: Helicidae)

Shell thickness in Theba pisana was measured in samples from Britain, northern France and the Mediterranean region. Mean adult thickness varied between about 0.08 mm and 0.20 mm. These values are much lower than previously published values. The considerable variation within samples was related to shell size, periods of growth, and resorption of shell material during breeding. Variation between samples was not great. This contrasts with previous work which linked shell thickness variation to large-scale climatic effects. Perhaps availability of calcium may be more important than climate in determining shell thickness in Theba Pisana .