Fam. 8.—Pompholygidae. Shell dextral, hyperstrophic, animal sinistral. Pompholyx. Choanomphalus.
Fam. 9.—Planorbidae. Visceral mass and shell sinistral; inferior pallial lobe very prominent, and transformed into a branchia. Planorbis, British. Bulinus. Miratesta.
Fam. 10.—Ancylidae. Shell conical, not spiral; inferior pallial lobe transformed into a branchia. Ancylus, British. Latia. Grundlachia.
Fam. 11.—Physidae. Visceral mass and shell sinistrally coiled; shell thin, with narrow aperture; no inferior pallial lobe. Physa, British. Aplexa, British.
Sub-order 2.—Stylommatophora. Pulmonata with two pairs of tentacles, except Janellidae and Vertigo; these tentacles are invaginable, and the eyes are borne on the summits of the posterior pair. Male and female genital apertures open into a common vestibule, except in Vaginulidae and Oncidiidae. Except in Oncidium, there is no longer a veliger stage in development.
Tribe 1.—Holognatha. Jaw simple, without a superior appendage.
Fam. 1.—Selenitidae. Radula with elongated and pointed teeth, like those of the Agnatha; a jaw present. Plutonia. Trigonochlamys.
Fam. 2.—Zonitidae. Shell external, smooth, heliciform or flattened; radula with pointed marginal teeth. Zonites, British. Ariophanta. Orpiella. Vitrina. Helicarion.
Fam. 3.—Limacidae. Shell internal. Limax, British. Parmacella. Urocyclus. Parmarion. Amalia. Agriolimax. Mesolimax. Monochroma. Paralimax. Metalimax.
Fam. 4.—Philomycidae. No shell; mantle covers the whole surface of the body; radula with squarish teeth. Philomycus.