Molluscs are soft-bodied invertebrates, which can be found in terrestrial, freshwater and marine habitats. The Phylum Mollusca is large and diverse, including terrestrial slugs and snails, bivalves, chitons, sea snails, nudibranchs, limpets and Cephalopods (octopus, cuttlefish and squid).


The Yorkshire Conchological Society, affiliated to the YNU, concentrates on land and freshwater snails and slugs.


The group records the distribution of land Mollusca and maintains county species databases and distribution maps.