In some Pulmonata (snails) the foot is extended at right angles to the visceral hump, which rises from it in the form of a coil as in Streptoneura; in others the visceral hump is not elevated, but is extended with the foot, and the shell is small or absent (slugs).
In aquatic Pulmonata the osphradium is retained.
The Pulmonata are, like the other Euthyneura, hermaphrodite, with elaborately developed copulatory organs and accessory glands.
The Pulmonata have a straight visceral nerve-loop, usually no operculum even in the embryo, and a multidenticulate radula, the teeth being equi-formal; and they are hermaphrodite.
Thus the whole of the Pulmonata (which breathe air, are destitute of gill-plumes and operculum and have a complicated hermaphrodite reproductive system) are either snails or slugs.
The same general range of body-form is shown in Pulmonata as in the Heteropoda and in the Opisthobranchia; at one extreme we have snails with coiled visceral hump, at the other cylindrical or flattened slugs (see fig.
The adaptation of the Pulmonata to terrestrial life has entailed little modification of the internal organization.
This conclusion has shown that the Euthyneura do not represent an archaic form of Gastropoda, but are themselves derived from streptoneurous forms. The difference between the two sub-classes has been shown to be slight; certain of the more archaic Tectibranchia (Actaeon) and Pulmonata (Chilina) still have the visceral commissure long and not untwisted.
The generative apparatus of the snail (Helix) may serve as an example of the hermaphrodite apparatus common to the Pulmonata and Opisthobranchia (fig.
The species of Helix are all herbivorous, like the Pulmonata generally; snails and slugs are well-known enemies to the gardener.