<zoology> An extensive division, or sub-class, of hermaphrodite gastropods, in which the mantle cavity is modified into an air-breathing organ, as in Helix, or land snails, Limax, or garden slugs, and many pond snails, as Limnaea and Planorbis.

Origin: NL, from L. Pulmo, -onis, a lung.

(01 Mar 1998)