Abyssochrysidae Tomlin, 1927 (current name source)
Acanthinulidae Steenberg, 1917 accepted as Valloniidae (source of synonymy)
Acanthonematidae Wenz, 1938 † (extant flag source)
Acanthonematidae Wenz, 1938 † (current name source)
Acavidae Pilsbry, 1895 (current name source)
Achatinellidae Gulick, 1873 (current name source)
Achatinidae Swainson, 1840 (current name source)
Aciculidae Gray, 1850 (current name source)
Aclididae G.O. Sars, 1878 (current name source)
Acmaeidae Forbes, 1850 (current name source)
Acmeidae Pollonera, 1905 accepted as Aciculidae Gray, 1850 (source of synonymy)
Acmeidae Pollonera, 1905 accepted as Aciculidae Gray, 1850 (basis of record)
Acochlidiidae Küthe, 1935 (current name source)
Acroloxidae Thiele, 1931 (current name source)
Acroreiidae Cossmann, 1893 † (current name source)
Acroreiidae Cossmann, 1893 † (extant flag source)
Acroreiidae Cossmann, 1893 † (basis of record)
Acteocinidae Dall, 1913 † (source of synonymy)
Acteonellidae Gill, 1871 † (extant flag source)
Acteonellidae Gill, 1871 † (current name source)
Acteonidae d'Orbigny, 1835 (current name source)
Acteoninidae Cossmann, 1895 † (extant flag source)
Acteoninidae Cossmann, 1895 † (current name source)
Actinocyclidae O'Donoghue, 1929 (current name source)
Addisoniidae Dall, 1882 (current name source)
Adeorbidae Monterosato, 1884 accepted as Tornidae Sacco, 1896 (source of synonymy)
Aeolidiidae Gray, 1827 (current name source)
Aglajidae Pilsbry, 1895 (current name source)
Agriolimacidae H. Wagner, 1935 (current name source)
Aillyidae (current name source)
Akeridae Mazzarelli, 1891 (current name source)
Aldanellidae Linsley & Kier, 1984 † (extant flag source)
Aldanellidae Linsley & Kier, 1984 † (current name source)
Amastridae (current name source)
Amathinidae Ponder, 1987 (current name source)
Amberleyidae Wenz, 1938 † (extant flag source)
Amberleyidae Wenz, 1938 † (current name source)
Ammonitellidae Pilsbry, 1930 accepted as Megomphicidae (source of synonymy)
Amnicolidae Tryon, 1863 (current name source)
Ampezzanildidae Bandel, 1995 † (current name source)
Ampezzanildidae Bandel, 1995 † (basis of record)
Ampezzanildidae Bandel, 1995 † (extant flag source)
Amphibolidae Hubendick, 1945 (current name source)
Amphibulimidae P. Fischer, 1873 (source of synonymy)
Amphiperatidae Gray, 1853 accepted as Ovulidae Fleming, 1822 (source of synonymy)
Amphitomariidae Bandel, 1994 † (extant flag source)
Amphitomariidae Bandel, 1994 † (basis of record)
Amphitomariidae Bandel, 1994 † (current name source)
Ampullariidae Gray, 1824 (current name source)
Ampullinidae Cossmann, 1918 (basis of record)
Ampullinidae Cossmann, 1918 (current name source)
Ampullospiridae Cox, 1930 accepted as Ampullinidae Cossmann, 1918 (source of synonymy)
Anabathridae Keen, 1971 (current name source)
Anadenidae (basis of record)
Anadenidae (current name source)
Anadromidae † (extant flag source)
Anadromidae † (current name source)
Anastomopsidae † (current name source)
Anastomopsidae † (basis of record)
Anastomopsidae † (extant flag source)
Anatomidae McLean, 1989 (current name source)
Ancylidae Rafinesque, 1815 accepted as Planorbidae Rafinesque, 1815 (source of synonymy)
Annulariidae Henderson & Bartsch, 1920 (additional source)
Anomphalidae Wenz, 1938 † (extant flag source)
Anopsiidae Pruvot-Fol, 1922 accepted as Hydromylidae Pruvot-Fol, 1942 (source of synonymy)
Anoptychiidae Bandel, 1995 † (current name source)
Anoptychiidae Bandel, 1995 † (extant flag source)
Anozygidae † (extant flag source)
Anozygidae † (current name source)
Anthracopupidae † (current name source)
Anthracopupidae † (extant flag source)
Aplustridae Gray, 1847 (current name source)
Aplysiidae Lamarck, 1809 (current name source)
Aporrhaidae Gray, 1850 (current name source)
Aranucidae Odhner, 1936 accepted as Tritoniidae Lamarck, 1809 (current name source)
Archaeopragidae Horný, 1963 † (extant flag source)
Archaeopragidae Horný, 1963 † (current name source)
Archidorididae Bergh, 1891 accepted as Dorididae Rafinesque, 1815 (source of synonymy)
Archinacellidae Knight, 1956 † (extant flag source)
Archinacellidae Knight, 1956 † (current name source)
Architectonicidae J.E. Gray in M.E. Gray, 1850 (current name source)
Argnidae (current name source)
Ariolimacidae (current name source)
Ariolimacidae (basis of record)
Arionidae (current name source)
Ariophantidae Godwin-Austen, 1883 (current name source)
Arminidae Iredale & O'Donoghue, 1923 (1841) (current name source)
Arthessidae C.R. Boettger, 1963 accepted as Volvatellidae Pilsbry, 1895 (source of synonymy)
Assimineidae H. Adams & A. Adams, 1856 (current name source)
Asteronotidae Thiele, 1931 accepted as Discodorididae Bergh, 1891 (source of synonymy)
Asterophilidae Thiele, 1925 accepted as Eulimidae Philippi, 1853 (source of synonymy)
Ataphridae Cossmann, 1918 (current name source)
Athoracophoridae (current name source)
Atlantidae Rang, 1829 (current name source)
Atydidae Thiele, 1925 accepted as Haminoeidae Pilsbry, 1895 (source of synonymy)
Babyloniidae Kuroda, Habe & Oyama, 1971 (current name source)
Baicaliidae P. Fischer, 1885 accepted as Amnicolidae Tryon, 1863 (source of synonymy)
Baptodorididae Odhner, 1926 accepted as Discodorididae Bergh, 1891 (source of synonymy)
Barleeiidae Gray, 1857 (current name source)
Bathydorididae Bergh, 1891 (current name source)