Why not look into a good book? ;)
"The Biology of Terrestrial Molluscs" - Barker,
G.M. (Ed.), Cabi Publishing, Wallingford, Oxon, Britain, 2001.
"Molluscs as Crop Pests" - Barker, G.M. (ed.), Cabi Publishing, Wallingford, Oxon, Britain, 2002.
"Natural Enemies of Terrestrial Molluscs" - Barker, G.M. (Ed.), Cabi Publishing, Wallingford, Oxon, Britain, 2004.
"Land Snails of Britain and North-West Europe" - Kerney,
M.P.; Cameron, R.A.D.; Collins,
"Land Snails of the British Isles" - A.A. Wardhaugh. Shire Natural History 1989. Short Guide on British land snails.
"Shells - Guide to the Jewels of the Sea" - Gabbi, G., Abbeville Press, New York, 2000.
"Atlas of the Land and Freshwater Molluscs of Britain and Ireland" - Kerney, M., Harley, Colchester, Britain, 1999.
"The Land and Freshwater Molluscs of Suffolk" - Killeen, Ian J., Ipswich, Britain, 1992. Atlas of the Suffolk land and freshwater molluscs with a map for every species and very good photographic illustrations of the most species.
"Land Snails of British Columbia" - Forsyth, R.G., Victoria, Canada, 2004. A very good book on the land snails of the Canadian state of British Columbia, including lots of additional information on snails in general.
Tables from Geyer, D. (1929): "Unsere Land- und Süßwassermollusken".