Abyssochrysos Tomlin, 1927 (basis of record)
Abyssochrysos Tomlin, 1927 (extant flag source)
Acanthomenia Thiele, 1913 (basis of record)
Acanthomenia Thiele, 1913 (extant flag source)
Acanthopleura Guilding, 1829 (basis of record)
Acanthopsole Trinchese, 1874 accepted as Facelina Alder & Hancock, 1855 (extant flag source)
Acanthopsole Trinchese, 1874 accepted as Facelina Alder & Hancock, 1855 (basis of record)
Acavus de Montfort, 1810 (basis of record)
Acavus de Montfort, 1810 (extant flag source)
Acharax Dall, 1908 (basis of record)
Achatina Lamarck, 1799 (extant flag source)
Achatina Lamarck, 1799 (basis of record)
Achatinella Swainson, 1828 (basis of record)
Achatinella Swainson, 1828 (extant flag source)
Acicula Risso, 1826 (extant flag source)
Acicula Risso, 1826 (basis of record)
Acila H. Adams & A. Adams, 1858 (basis of record)
Aciodoris Martens, 1881 (basis of record)
Aciodoris Martens, 1881 (extant flag source)
Acmaea Eschscholtz, 1833 (basis of record)
Acostaea d'Orbigny, 1851 (extant flag source)
Acostaea d'Orbigny, 1851 (basis of record)
Acroloxus Beck, 1838 (basis of record)
Acrosterigma Dall, 1900 (basis of record)
Actaeocina accepted as Acteocina Gray, 1847 (basis of record)
Actaeocina accepted as Acteocina Gray, 1847 (extant flag source)
Actinocyclis (basis of record)
Actinocyclis (extant flag source)
Actinonaias Crosse & P. Fischer, 1894 (basis of record)
Actinonaias Crosse & P. Fischer, 1894 (extant flag source)
Adacna Eichwald, 1838 (extant flag source)
Adacna Eichwald, 1838 (basis of record)
Adamussium Thiele, 1934 (basis of record)
Adamussium Thiele, 1934 (extant flag source)
Adelopoma Doering, 1885 (basis of record)
Adelopoma Doering, 1885 (extant flag source)
Adontorhina Berry, 1947 (basis of record)
Adrana H. Adams & A. Adams, 1858 (basis of record)
Adula H. Adams & A. Adams, 1857 (basis of record)
Afroditropis Bequaert & Clench, 1936 (extant flag source)
Afroditropis Bequaert & Clench, 1936 (basis of record)
Agaronia Gray, 1839 (basis of record)
Agyrodonax (basis of record)
Agyrodonax (extant flag source)
Aillya Odhner, 1927 (extant flag source)
Aillya Odhner, 1927 (basis of record)
Alasmidonta Say, 1818 (basis of record)
Alcadia Gray, 1840 (basis of record)
Alcadia Gray, 1840 (extant flag source)
Alectryonella Sacco, 1897 (basis of record)
Alexiana (extant flag source)
Alexiana (basis of record)
Alloiodoris Bergh, 1904 (basis of record)
Alloiodoris Bergh, 1904 (extant flag source)
Alloposus Verrill, 1880 accepted as Haliphron Steenstrup, 1859 (extant flag source)
Alloposus Verrill, 1880 accepted as Haliphron Steenstrup, 1859 (basis of record)
Alycaeus Baird, 1850 (extant flag source)
Alycaeus Baird, 1850 (basis of record)
Amaea H. Adams & A. Adams, 1853 (basis of record)
Amastra Adams, 1855 (basis of record)
Amastra Adams, 1855 (extant flag source)
Amauropsis Mörch in Rink, 1857 (basis of record)
Amblema Rafinesque, 1820 (basis of record)
Amblema Rafinesque, 1820 (extant flag source)
Amblychilepas Pilsbry in Tryon & Pilsbry, 1890 (basis of record)
Amiantis Carpenter, 1864 (basis of record)
Amicula Gray, 1847 (basis of record)
Ammonitella Cooper, 1869 (extant flag source)
Ammonitella Cooper, 1869 (basis of record)
Amphibulima Lamarck, 1805 (extant flag source)
Amphibulima Lamarck, 1805 (basis of record)
Amphichaena Philippi, 1847 accepted as Donax Linnaeus, 1758 (basis of record)
Amphicyclotus Crosse & Fischer, 1879 (basis of record)
Amphicyclotus Crosse & Fischer, 1879 (extant flag source)
Amphidromus Albers, 1850 (basis of record)
Amphidromus Albers, 1850 (extant flag source)
Amphigyra Pilsbry, 1906 (basis of record)
Amphigyra Pilsbry, 1906 (extant flag source)
Amphimelania P. Fischer, 1885 accepted as Holandriana Bourguignat, 1884 (extant flag source)
Amphimelania P. Fischer, 1885 accepted as Holandriana Bourguignat, 1884 (basis of record)
Amphitretus Hoyle, 1885 (basis of record)
Amphitretus Hoyle, 1885 (extant flag source)
Amphorina Quatrefages, 1844 accepted as Eubranchus Forbes, 1838 (extant flag source)
Amphorina Quatrefages, 1844 accepted as Eubranchus Forbes, 1838 (basis of record)
Amusium Röding, 1798 (basis of record)
Anadara Gray, 1847 (basis of record)
Analogium Risbec, 1928 accepted as Gymnodoris Stimpson, 1855 (basis of record)
Analogium Risbec, 1928 accepted as Gymnodoris Stimpson, 1855 (extant flag source)
Anapella Dall, 1895 (basis of record)
Anatina Schumacher, 1817 (basis of record)
Anatinella Sowerby G. B II., 1833 (basis of record)
Anatinella Sowerby G. B II., 1833 (extant flag source)
Anceya Bourguignat, 1885 (extant flag source)
Anceya Bourguignat, 1885 (basis of record)
Ancilla Lamarck, 1799 (basis of record)
Ancula Lovén, 1846 (basis of record)
Ancula Lovén, 1846 (extant flag source)
Ancylus O. F. Müller, 1773 (basis of record)
Ancylus O. F. Müller, 1773 (extant flag source)
Aneitea Gray, 1860 (basis of record)