"Lower Heterobranchia" (basis of record)
Abbottellinae Watters, 2016 (status source)
Acanthinulinae Steenberg, 1917 accepted as Valloniidae E. S. Morse, 1864 (status source)
Acavidae Pilsbry, 1895 (basis of record)
Acavoidea Pilsbry, 1895 accepted as Rhytidoidea Pilsbry, 1893 (source of synonymy)
Acellinae Hannibal, 1912 accepted as Lymnaeinae Rafinesque, 1815 (source of synonymy)
Achatinellidae Gulick, 1873 (basis of record)
Achatinellinae Gulick, 1873 (basis of record)
Achatinidae Swainson, 1840 (basis of record)
Achatinina (basis of record)
Achatinini Swainson, 1840 (basis of record)
Achatinoidea Swainson, 1840 (basis of record)
Aciculidae J. E. Gray, 1850 (basis of record)
Acirsinae Cossmann, 1912 accepted as Epitoniidae S. S. Berry, 1910 (1812) (source of synonymy)
Aclididae G. O. Sars, 1878 accepted as Eulimidae R. A. Philippi, 1853 (source of synonymy)
Acmeidae Pollonera, 1905 accepted as Aciculidae J. E. Gray, 1850 (basis of record)
Acochlidiimorpha (basis of record)
Acochlidioidea Küthe, 1935 (basis of record)
Acremodontinae B. A. Marshall, 1983 accepted as Trochaclididae Thiele, 1928 (source of synonymy)
Acrillinae Jousseaume, 1912 accepted as Epitoniidae S. S. Berry, 1910 (1812) (source of synonymy)
Acteocinidae Dall, 1913 accepted as Tornatinidae P. Fischer, 1883 (source of synonymy)
Acteonellidae Gill, 1871 † (basis of record)
Acteonelloidea Gill, 1871 † (basis of record)
Acteonidae A. d'Orbigny, 1842 (basis of record)
Acteonimorpha (basis of record)
Actinocyclidae O'Donoghue, 1929 (basis of record)
Acusidae J. E. Gray, 1853 accepted as Terebridae Mörch, 1852 (source of synonymy)
Adelomelonini Pilsbry & Olsson, 1954 (basis of record)
Adustinae Cotton & Steadman, 1946 accepted as Erroneinae F. A. Schilder, 1927 (source of synonymy)
Aegiridae P. Fischer, 1883 (basis of record)
Aegistini Kuroda & Habe, 1949 (basis of record)
Aegopinella Lindholm, 1927 (taxonomy source)
Aeolidioidea Gray, 1827 (basis of record)
Afropominae Berthold, 1991 accepted as Ampullariinae J. E. Gray, 1824 (basis of record)
Aillyidae H. B. Baker, 1955 (additional source)
Aiptospirinae X.-J. Wang, 1980 † (additional source)
Aitengidae Swennen & Buatip, 2009 (basis of record)
Akeroidea Mazzarelli, 1891 (basis of record)
Aldisidae Odhner, 1939 accepted as Cadlinidae Bergh, 1891 (basis of record)
Alycaeinae W. T. Blanford, 1864 (basis of record)
Amaltheidae Dall, 1889 accepted as Hipponicidae Troschel, 1861 (source of synonymy)
Amastridae Pilsbry, 1910 (basis of record)
Amastrinae Pilsbry, 1910 (basis of record)
Amathinidae Ponder, 1987 (basis of record)
Amberleya J. Morris & Lycett, 1851 † (subsequent type designation)
Amberleyidae Wenz, 1938 † accepted as Eucyclidae Koken, 1896 (additional source)
Ammonitellidae Pilsbry, 1930 accepted as Megomphicidae H. B. Baker, 1930 (source of synonymy)
Ammonitellinae Pilsbry, 1930 accepted as Megomphicidae H. B. Baker, 1930 (source of synonymy)
Amoriinae J. E. Gray, 1857 (basis of record)
Amoriini J. E. Gray, 1857 (basis of record)
Ampezzanildidae Bandel, 1994 † (basis of record)
Ampezzonaticopsinae Bandel, 2007 † (basis of record)
Ampezzopleura Bandel, 1991 † (subsequent type designation)
Ampezzopleurinae Nützel, 1998 † (basis of record)
Amphibulimidae P. Fischer, 1873 (basis of record)
Amphidrominae Kobelt, 1902 accepted as Camaeninae Pilsbry, 1895 (source of synonymy)
Amphigastropoda † (taxonomy source)
Amphiperatidae J. E. Gray, 1853 accepted as Ovulidae J. Fleming, 1822 (source of synonymy)
Amphitomariidae Bandel, 1994 † (basis of record)
Ampullaceridae Troschel, 1845 accepted as Amphibolinae J. E. Gray, 1840 (basis of record)
Ampullariidae J. E. Gray, 1824 (additional source)
Anabathridae Keen, 1971 (basis of record)
Anadenidae Pilsbry, 1948 (basis of record)
Anatominae J. H. McLean, 1989 accepted as Anatomidae J. H. McLean, 1989 (basis of record)
Ancistrobasidae Bandel, 2010 accepted as Fluxinellini B. A. Marshall, 1991 (source of synonymy)
Ancylodorididae Thiele, 1926 accepted as Onchidorididae Gray, 1827 (basis of record)
Andangulariinae Nützel & Erwin, 2004 † (basis of record)
Andoniinae Vera-Peláez, 2002 † accepted as Raphitomidae Bellardi, 1875 (source of synonymy)
Andronakiinae Schileyko, 1998 accepted as Enini B. B. Woodward, 1903 (1880) (source of synonymy)
Angariidae J. E. Gray, 1857 (basis of record)
Anisocyclidae van Aartsen, 1995 accepted as Eulimellini Saurin, 1958 represented as Turbonillinae Bronn, 1849 (basis of record)
Anisomyonidae Kanie, 1975 † accepted as Siphonariidae J. E. Gray, 1827 (source of synonymy)
Anoglyptidae Iredale, 1937 accepted as Caryodidae Connolly, 1915 (source of synonymy)
Anomphalidae Wenz, 1938 † (basis of record)
Anopsiidae Pruvot-Fol, 1922 accepted as Hydromylidae Pruvot-Fol, 1942 (1862) (source of synonymy)
Anoptychia Koken, 1892 † (status source)
Anoptychia supraplecta (Münster, 1841) † (status source)
Anoptychiidae Bandel, 1994 † accepted as Zygopleurinae Wenz, 1938 † (source of synonymy)
Ansolidae Slavoshevskaya, 1975 accepted as Barleeiidae J. E. Gray, 1857 (basis of record)
Antiopellidae Odhner, 1934 accepted as Janolidae Pruvot-Fol, 1933 (source of synonymy)
Antiopidae Locard, 1886 accepted as Janolidae Pruvot-Fol, 1933 (basis of record)
Antonellini C. M. Cooke & Y. Kondo, 1961 (basis of record)
Aperidae Möllendorff, 1903 accepted as Chlamydephorinae T. D. A. Cockerell, 1935 (1903) (source of synonymy)
Aplodontidae Kuroda, 1933 accepted as Modulidae P. Fischer, 1884 (basis of record)
Aplysiida (basis of record)
Aplysioidea Lamarck, 1809 (basis of record)
Aptyxiellidae Hacobjan, 1973 † accepted as Nerinellidae Pchelintsev, 1960 † (source of synonymy)
Aquillidae Pilsbry, 1904 accepted as Cymatiidae Iredale, 1913 (1854) (status source)
Araeonematidae Nützel, 2012 † (basis of record)
Aranucidae Odhner, 1936 accepted as Tritoniinae Lamarck, 1809 (basis of record)
Archaegopis Wenz, 1915 † (additional source)
Archaeogastropoda accepted as Vetigastropoda (status source)
Archaeophialidae Knight & Yochelson, 1958 † (basis of record)
Archaeozonitidae Pfeffer, 1930 † (additional source)
Archicypraeinae F. A. Schilder, 1927 † accepted as Gisortiinae F. A. Schilder, 1927 † (source of synonymy)
Archimediellidae Starobogatov, 1982 accepted as Turritellinae Lovén, 1847 (status source)
Architaenioglossa (additional source)
Architectonicidae J. E. Gray, 1850 (basis of record)
Architectonicoidea J. E. Gray, 1850 (basis of record)
Arculariidae Iredale, 1915 accepted as Nassariinae Iredale, 1916 (1835) (status source)

Abrolhos Archipelago, Brazil for Zoila ketyana bataviensis Lorenz & H. Morrison, 2001 
Indian Exclusive Economic Zone for Madrella ferruginosa Alder & Hancock, 1864 
Slovenia for Paludinella fontinalis F. J. Schmidt, 1847 

 Authority

 for Septariidae Jousseaume, 1894

Golikov & Starobogatov (1975) declared this family as new though the true author of this taxon is Jousseaume ... [details]

 Authority

 for Septariidae Jousseaume, 1894

Golikov & Starobogatov (1975) declared this family as new though the true author of this taxon is Jousseaume ... [details]

 Classification

 for Mesocochliopidae X.-H. Yu, 1987 †

Mesocochliopa was originally classified as a genus of Amnicolidae by Yen & Reeside (1946) and was also listed as a ... [details]

 Homonymy

 for Cepolidae Ihering, 1909

Cepolidae Ihering, 1909 is a junior homonym of Cepolidae Rafinesque, 1815 [Pisces]. The case will be referred to ... [details]

 Nomenclature

 for Babyloniidae Kuroda, Habe & Oyama, 1971

Two family-group names are older than Babyloniidae. Swainson based his concept of Eburninae on species of ... [details]

 Nomenclature

 for Cerastua Strand, 1928

Cerastua Strand, 1928 was proposed as a replacement name for Cerastus E. von Martens, 1860 (non Dejean, 1821, ... [details]

 Nomenclature

 for Cerastuidae Wenz, 1930

Cerastuidae was based on Cerastua Strand, 1928, an unnecessary replacement name for Ceratsus E. von Martens, 1860. [details]

 Nomenclature

 for Cionellidae L. Pfeiffer, 1879

When he established Cochlicopidae, Pilsbry (1900) did not justify his action. Later, he (Pilsbry, 1908 [in ... [details]

 Nomenclature

 for Ficus Röding, 1798

Röding listed "Bulla ficus" [Murex ficus Linnaeus, 1758] in the synonymy of Ficus communis Röding, 1798, and ... [details]

 Nomenclature

 for Umboniinae H. Adams & A. Adams, 1854 (1840)

Takes precedence from Rotellinae Swainson, 1840 [details]

 Spelling

 for Anostomopsidae H. Nordsieck, 1986 †

The spelling "Anastomopsidae" as used in the literature is based on Anastomopsis, an incorrect subsequent spelling ... [details]

 Taxonomic remark

 for Graphidulidae Stephenson, 1941 †

Name only, no diagnosis. Not available under Art. 13.2.1, unless discovery of an author who used the name before 2000 [details]

 Taxonomic remark

 for Orthopoma J. E. Gray, 1868

The genus name Orthopoma was established without any included species, and it appears that none was ever ... [details]

 Type species

 for Anoptychia Koken, 1892 †

For uncertainties concerning the type species, see the discussion by Bouchet et al. (2017). [details]