Wikipedia
Sigmurethra
Sigmurethra is a taxonomic category of air-breathing land snails and slugs, terrestrial pulmonate gastropod molluscs. This is an Informal Group which includes the majority of land snails and slugs.
The two strong synapomorphies of Sigmurethra are a long pedal gland placed beneath a membrane and retractile tentacles.
Several families in this group contain species of snails and slugs that create love darts.
Sigmurethra are known from the Cretaceous to the Recent periods.
In the taxonomy of the Gastropoda by Bouchet & Rocroi, 2005, Sigmurethra is an "Informal Group", a subsection of the Stylommatophora.