The Pulmonata, or "pulmonates", are an informal group (previously an order, and before that a subclass) of snails and slugs characterized by the ability to breathe air, by virtue of having a pallial lung instead of a gill, or gills. The group includes many land and freshwater families, and several marine families.
The taxon Pulmonata as traditionally defined was found to be polyphyletic in a molecular study per Jörger et al., dating from 2010.
Pulmonates have a single auricle and kidney, and a concentrated, symmetrical, nervous system. The mantle cavity is located on the right side of the body, and lacks gills, instead being converted into a vascularised lung. Most species have a shell, but no operculum, although the group does also include several shell-less slugs. Pulmonates are hermaphroditic, and some groups possess love darts.
Shells of pulmonate styllomatophoran snails in a museum collection
An artistic but scientifically incorrect version of various European land snails and slugs (one species here is not a pulmonate), their food plants and fungi, and a beetle that eats mollusks, bottom right.
Holznagel, W. E.; Colgan, D. J.; Lydeard, C. (2010). "Pulmonate phylogeny based on 28S rRNA gene sequences: A framework for discussing habitat transitions and character transformation". Molecular Phylogenetics and Evolution57 (3): 1017–1025. doi:10.1016/j.ympev.2010.09.021. PMID20920591.edit