as aquatic, terrestrial or intermediate, and an indication is given where it is thought that the species is introduced. Species are considered to be native, unless otherwise indicated; that information is mostly taken from Kerney, and Rowson et al. The status and taxonomy of freshwater gastropods has been updated according to Rowson et al. (2021). Gastropoda Neritidae – aquatic (also tolerates brackish water) Theodoxus fluviatilis fluviatilis (Linnaeus, 1758) Aciculidae – terrestrial Acicula fusca (Montagu, 1803) Viviparidae (river snails) – aquatic Viviparus viviparus (Linnaeus, 1758) Assimineidae – terrestrial (intermediate marine) Assiminea grayana Fleming, 1828 – introduced Truncatellidae – terrestrial (intermediate marine) Truncatella subcylindrica (Linnaeus, 1758) Bithyniidae – aquatic Bithynia leachii (Sheppard, 1823) Bithynia tentaculata (Linnaeus, 1758) Potamopyrgidae – aquatic Potamopyrgus antipodarum (Gray, 1843) – introduced Hydrobiidae – aquatic (some are arguably marine) Hydrobia acuta (Draparnaud, 1805) – subspecies: Hydrobia acuta neglecta Muus, 1963 Ecrobia ventrosa (Montagu, 1803) – synonym: Ventrosia ventrosa Peringia ulvae (Pennant, 1777) Mercuria anatina (Poiret, 1801) – synonyms: M. confusa auct. non Frauenfeld, 1863, M. similis auct. non (Draparnaud, 1805) Valvatidae (valve snails) – aquatic Valvata cristata O.F. Müller, 1774 Valvata piscinalis (O.F. Müller, 1774) Pomatiidae (land winkles) – terrestrial Pomatias elegans (O.F. Müller, 1774) The following gastropods are pulmonates: Ellobiidae (hollow-shelled snails) – terrestrial or semi-marine Carychium minimum O.F. Müller, 1774 Carychium tridentatum (Risso, 1826) Leucophytia bidentata (Montagu, 1808) Myosotella denticulata (Montagu, 1803) Myosotella myosotis (Draparnaud, 1801) Otinidae – aquatic (almost fully marine, but a pulmonate) Otina ovata (Brown, 1827) Lymnaeidae – aquatic Ampullaceana balthica (Linnaeus, 1758) – synonyms: Radix balthica, Radix peregra auct. non (O.F. Müller, 1774) Galba truncatula (O.F. Müller, 1774) Lymnaea stagnalis (Linnaeus, 1758) Myxas glutinosa (O.F. Müller, 1774) E Omphiscola glabra (O.F. Müller, 1774) – found in 2009 at one site in the SE of Ireland, but listed as extinct on a local red list (2009). Radix auricularia (Linnaeus, 1758) Stagnicola fuscus (C. Pfeiffer, 1821) – synonym: Lymnaea fusca Physidae (bladder snails) – aquatic Aplexa hypnorum (Linnaeus, 1758) Physa fontinalis (Linnaeus, 1758) Physella acuta (Draparnaud, 1805) = Physella heterostropha (Say, 1817) – introduced Physella gyrina (Say, 1821) – introduced Planorbidae (ramshorn snails) – aquatic Ancylus fluviatilis (O.F. Müller, 1774) Anisus leucostoma (Millet, 1813) Anisus vortex (Linnaeus, 1758) Anisus vorticulus (Troschel, 1834) Anisus spirorbis (Linnaeus, 1758) Bathyomphalus contortus (Linnaeus, 1758) Gyraulus albus (O.F. Müller, 1774) Gyraulus crista (Linnaeus, 1758) Gyraulus laevis (Alder, 1838) Hippeutis complanatus (Linnaeus, 1758) Planorbarius corneus corneus (Linnaeus, 1758) Planorbis carinatus