The subclass Pulmonata includes all mollusks breathing air. They are normal gastropods, having a broad foot and usually, a large spiral, inoperculate shell. Although mostly terrestrial, a
few aquatic and a number of fluviatile forms are here included. There are no marine species, but the Auriculidae are in great part inhabitants of seashores where, at hightide, they are covered by the waters. As to food, some are carnivorous, but the sub class is, as a rule, phytophagous. The teeth are numerous, similar, recurved, aculeated or dentate at the extremity, with broad pavimental bases. These teeth are developed many in a row, upon a broad lingual ribbon ; when the rows are straight the teeth are similar throughout, when curved or angulated the forms of the teeth become more or less changed. There is usually a single, rather conspicuous upper jaw, composed of one or of three pieces never of two pieces as in the branchiferous mollusks. Sexes united in each individual, but the union of two individ
uals required for mutual impregnation. Genital orifices sometimes contiguous, opening in a common cloaca, sometimes distinct.

The Pulmonata are related to phytophagous sea-snails through the Cyclostomae or operculated landsnails, and the Ampullariae, to the limpets through Gadinia, Siphonaria, to the nudibranchs
through Onchidium.