Aaleniella Plumhoff, 1963 † (status source)
Aaptolasma Newman & Ross, 1971 accepted as Hexelasma Hoek, 1913 (additional source)
Abathomphalus Bolli, Loeblich & Tappan, 1957 † (status source)
Abbottina McCulloch, 1977 accepted as Nonion de Montfort, 1808 (source of synonymy)
Abdullaevia Suleymanov, 1965 † (status source)
Aberrapex Jensen, 2001 (status source)
Abludogammarus G. Karaman, 1980 (status source)
Abortivelum Berdan & Copeland, 1973 † (status source)
Abrardia Neumann & Damotte, 1960 † (status source)
Abrobairdia Chen in Chen & Shi, 1982 † (status source)
Absina Gründel, 1962 † (status source)
Absonocytheropteron Puri, 1957 † (status source)
Abuhammadina Abd-Elshafy & Ibrahim, 1990 † (status source)
Abylopsoides Sears, 1953 accepted as Abylopsis Chun, 1888 (source of synonymy)
Abyssamina Schnitker & Tjalsma, 1980 † (status source)
Abyssochiton Dell'Angelo & Palazzi, 1989 accepted as Ferreiraella Sirenko, 1988 (source of synonymy)
Abyssocythereis Schornikov, 1975 (status source)
Abyssotrema Campbell, 1975 accepted as Steringophorus Odhner, 1905 (source of synonymy)
Acamptochetus Cossmann, 1901 † accepted as Metula H. Adams & A. Adams, 1853 (source of synonymy)
Acamptogorgia Wright & Studer, 1889 accepted as Villogorgia Duchassaing & Michelloti, 1862 (source of synonymy)
Acandela Stechow, 1920 accepted as Candelabrum de Blainville, 1830 (source of synonymy)
Acanthastraea Milne Edwards & Haime, 1848 accepted as Acanthastrea Milne Edwards & Haime, 1848 (source of synonymy)
Acanthastrea Milne Edwards & Haime, 1848 (status source)
Acanthelia Wells, 1937 † accepted as Echinopora Lamarck, 1816 (source of synonymy)
Acanthephyra A. Milne-Edwards, 1881 (status source)
Acanthobatis Larrazet, 1886 † accepted as Anacanthobatis von Bonde & Swart, 1923 (source of synonymy)
Acanthochasmus Looss, 1901 accepted as Acanthostomum Looss, 1899 (source of synonymy)
Acanthococcus Lagerheim, 1883 accepted as Glochiococcus G.B. De Toni in G.B. De Toni & D. Levi, 1888 (source of synonymy)
Acanthocollaritrema Travassos, Teixeira de Freitas & Bührnheim, 1965 (status source)
Acanthocolpoides Travassos, Teixeira de Freitas & Buhrnheim, 1965 accepted as Prodistomum Linton, 1910 (additional source)
Acanthocythere Sylvester-Bradley, 1956 † (status source)
Acanthodesiomorpha d'Hondt, 1981 (status source)
Acanthogalea Gibson, 1976 (status source)
Acanthonotozoma Boeck, 1876 (status source)
Acanthonotozomella Schellenberg, 1926 (status source)
Acanthonotozomoides Schellenberg, 1931 (status source)
Acanthonotus Ross in Ross, 1835 accepted as Acanthonotozoma Boeck, 1876 (source of synonymy)
Acanthonyx Latreille, 1828 (status source)
Acanthoparyphium Dietz, 1909 (status source)
Acanthopharynx Reisinger, 1924 (status source)
Acanthophrys A. Milne-Edwards, 1865 (status source)
Acanthopora Verrill, 1864 † accepted as Echinopora Lamarck, 1816 (source of synonymy)
Acanthopsole Trinchese, 1874 accepted as Facelina Alder & Hancock, 1855 (source of synonymy)
Acanthopsolus Odhner, 1905 accepted as Neophasis Stafford, 1904 (source of synonymy)
Acanthopus De Haan, 1833 accepted as Percnon Gistel, 1848 (source of synonymy)
Acanthostylotella Burton & Rao, 1932 (status source)
Acanthotrigonia van Hoepen, 1929 † (status source)
Acanthuritrema Yamaguti, 1970 (status source)
Acarinina Subbotina, 1953 † (status source)
Accordiella Farinacci, 1962 † (status source)
Acerointestinecola Jahan, 1970 accepted as Stomachicola Yamaguti, 1934 (source of synonymy)
Acerominyas Andres, 1884 (status source)
Acerrotrupa Yu & Wang, 1981 † (status source)
Acervoschwagerina Hanzawa, 1949 † (status source)
Acetobacter Beijerinck, 1898 (Approved Lists, 1980) (status source)
Achaeopsis Stimpson, 1857 (status source)
Achaeus Leach, 1817 (status source)
Achiridota Clark, 1908 (status source)
Achnanthidium Kützing, 1844 (current name source)
Achoerus Vlasenko, 1931 accepted as Metadena Linton, 1910 (source of synonymy)
Achoerus Beklemischev, 1914 (status source)
Achromadora Cobb, 1913 (status source)
Aciculella Vyalov, 1968 † (status source)
Aciculina Vyalov, 1968 † accepted as Aciculella Vyalov, 1968 † (source of synonymy)
Aciculina Deshayes, 1861 † accepted as Eulimella Forbes & MacAndrew, 1846 (source of synonymy)
Acies Lesson, 1830 accepted as Porpita Lamarck, 1801 (source of synonymy)
Acinolaemus F. G. Thompson & Upatham, 1997 (status source)
Acmaeopleura Stimpson, 1858 (status source)
Acominia Finlay, 1926 accepted as Cominella Gray, 1850 (additional source)
Acontiactis England, 1990 (status source)
Acostata Brönniman, Whitaker & Valleri, 1992 † (status source)
Acraspedanthus Carlgren, 1924 (status source)
Acratia Delo, 1930 † (status source)
Acratina Egorov, 1953 † (status source)
Acremodactyla Kwietniewski, 1897 (status source)
Acremodonta B. A. Marshall, 1983 (status source)
Acremodontina B. A. Marshall, 1995 (status source)
Acreuciroa Jaeckel & Thiele, 1931 (status source)
Acrhelia Milne-Edwards & Haime, 1849 accepted as Galaxea Oken, 1815 (additional source)
Acrochordium Meyen, 1834 accepted as Zanclea Gegenbaur, 1856 (source of synonymy)
Acrocircus Lambert, 1911 † accepted as Triplacidia Bittner, 1891 † (source of synonymy)
Acrocythere Neale, 1960 † (status source)
Acrohelia Milne Edwards, 1857 accepted as Galaxea Milne Edwards, 1857 accepted as Galaxea Oken, 1815 (source of synonymy)
Acrostoma Brot, 1871 accepted as Paracrostoma Cossmann, 1900 † (source of synonymy)
Acroura Agassiz, 1835 † (status source)
Acrumena Brunet, 1965 (status source)
Actaecia Dana, 1853 (status source)
Actaeocina accepted as Acteocina Gray, 1847 (source of synonymy)
Actaeodius Klunzinger, 1913 accepted as Actaea De Haan in Siebold, 1833 (additional source)
Actaeonidea Gabb, 1872 † accepted as Rictaxis Dall, 1871 (additional source)
Acteocina Gray, 1847 (status source)
Actinocephalus Kützing, 1843 accepted as Hydrocoleum Kützing ex Gomont, 1892 (status source)
Actinocyclina Gümbel, 1870 † (status source)
Actinodactylus Duchassaing, 1850 (status source)
Actinodendron Quoy & Gaimard in de Blainville, 1830 (status source)
Actinodendrum Dana, 1846 accepted as Actinodendron Quoy & Gaimard in de Blainville, 1830 (source of synonymy)
Actinodiscus de Blainville, 1830 accepted as Discosoma Rüppell & Leuckart, 1828 (source of synonymy)
Actinoleberis McKenzie in Howe & McKenzie, 1989 (status source)
Actinolobopsis Verrill, 1899 (status source)
Actinometra Müller, 1841 accepted as Comatula Lamarck, 1816 (source of synonymy)