Gastropoda

Gastropoda (gastropod; phylum Mollusca) The class of Mollusca that includes snails and slugs. They have a true head, an unsegmented body, and a broad, flat foot. They appear in the Cambrian and occur in sedimentary rocks of all ages, occupying a range of aquatic and terrestrial environments. The majority of modern gastropods and all the fossil forms possess a coiled shell, which is all that is left to the palaeontologist for determining identification. The classification of living forms is based largely upon soft parts, so that similarly shaped shells developed by unrelated groups cause problems of nomenclature.