MATERIAL

The proposed morphometric approach has been established with gastropods of the family Helicidae (Gastropoda, Stylommatophora). Studied specimens are tightly coiled and slightly trochospiraled with a large overlap of successive whorls. All studied specimens come from and are deposited in the Zoological Museum of the University of Zürich. The different steps of the method will be illustrated with the case of one specimen belonging to the species Cepaea nemoralis (Linnaeus 1758). This grove snail or brown-lipped snail is a terrestrial pulmonate gastropod. It is one of the most common species of land snails in Europe. It is a relatively small snail, growing to a height of about 20 mm and a width of 25 mm. The semi-glossy shell grows up 4½ to 5½ whorls (Figure 2).