In Edward Forbes’ own words: ‘The snails are provided with spiral, often turreted, rarely depressed, or expanded shells, which, however, are never operculated. In the deficiency of operculum the animal, when hybernating, closes the orifice with a membranous epiphragm, perforated for the admission of air. The head is well-developed and furnished with retractile tentactula, the two upper ones always prominent and bearing the eyes at the extremities. These tentacles are always cylindrical.’ From ‘A History of British Mollusca and their Shells, by Forbes and Hanley (1853).
Right: Helix pomatia, the edible snail