Abyssascidia Herdman, 1880 (additional source)
Acabaria Gray, 1859 accepted as Melithaea Milne Edwards, 1857 (additional source)
Acanella Gray, 1870 (additional source)
Acanthastrea Milne Edwards & Haime, 1848 (additional source)
Acanthogorgia Gray, 1857 (additional source)
Acanthomuricea Hentschel, 1903 (additional source)
Acanthopriapulus van der Land, 1970 (additional source)
Acaulis Stimpson, 1853 (additional source)
Acauloides Bouillon, 1965 (additional source)
Achelia Hodge, 1864 (additional source)
Acheliana Arnaud, 1971 (additional source)
Acromitus Light, 1914 (basis of record)
Acrophytum Hickson, 1900 (additional source)
Acryptolaria Norman, 1875 (additional source)
Acthelmis Lütken, 1875 (additional source)
Actinarctus Schulz, 1935 (additional source)
Actinernus Verrill, 1879 (additional source)
Actinioides Haddon & Shackleton, 1893 (additional source)
Actinoposthia An der Lan, 1936 (additional source)
Actinoptilum Kükenthal, 1911 (additional source)
Actinoscyphia Stephenson, 1920 (additional source)
Actinostola Verrill, 1883 (additional source)
Adagnesia Kott, 1963 (additional source)
Adelopora Cairns, 1982 (additional source)
Adeloposthia An der Lan, 1936 accepted as Paraproporus Westblad, 1945 (additional source)
Adenocauda Dörjes, 1968 (additional source)
Aeginopsis Brandt, 1835 (additional source)
Aeginura Haeckel, 1879 (additional source)
Afronta Hyman, 1944 (additional source)
Agaricia Lamarck, 1801 (additional source)
Aglaoprimnoa Bayer, 1996 (additional source)
Agnesiopsis Monniot C., 1969 accepted as Corynascidia Herdman, 1882 (basis of record)
Agnezia Monniot C. & Monniot F., 1991 (additional source)
Aiptasiogeton Schmidt, 1972 (additional source)
Alca Linnaeus, 1758 (additional source)
Allantactis Danielssen, 1890 (additional source)
Alle Link, 1806 (additional source)
Alloeocarpa Michaelsen, 1900 (additional source)
Alloposus A. E. Verrill, 1880 accepted as Haliphron Steenstrup, 1859 (basis of record)
Alluna Faubel & Regier, 1983 (additional source)
Althoffia Lohmann, 1892 (additional source)
Alveopora Blainville, 1830 (additional source)
Amalosoma Fisher, 1948 (additional source)
Amalthaea Schmidt, 1852 accepted as Corymorpha M. Sars, 1835 (additional source)
Amaroucium Milne Edwards, 1841 accepted as Aplidium Savigny, 1816 (additional source)
Amblyiulus Silvestri, 1896 (additional source)
Ammothea Leach, 1814 (additional source)
Ammothella Verrill, 1900 (additional source)
Amphiacme Kükenthal, 1903 (additional source)
Amphilina Wagener, 1858 (additional source)
Amphioxus Yarrell, 1836 accepted as Branchiostoma Costa, 1834 (additional source)
Amphogona Browne, 1905 (additional source)
Anacropora Ridley, 1884 (additional source)
Ancistrocheirus Gray, 1849 (additional source)
Andvakia Danielssen, 1890 (additional source)
Anisolabis Fieber, 1853 (additional source)
Annatiara Russell, 1940 (additional source)
Annulipulsellum Scarabino, 1986 (additional source)
Anomocora Studer, 1878 (additional source)
Anomopera Hartmeyer, 1923 (additional source)
Anoropallene Stock, 1956 (additional source)
Anous Stephens, 1826 (additional source)
Antarctoscyphus Pena Cantero, Garcia Carrascosa & Vervoort, 1997 (additional source)
Anthogorgia Verrill, 1868 (additional source)
Anthohebella Boero, Bouillon & Kubota, 1997 (additional source)
Antholoba Hertwig, 1882 (additional source)
Anthomastus Verrill, 1878 (additional source)
Anthosactis Danielssen, 1890 (additional source)
Anthothela Verrill, 1879 (additional source)
Antigonaria Dörjes, 1968 (additional source)
Antillesoma Stephen & Edmonds, 1972 (additional source)
Antroposthia Faubel, 1974 (additional source)
Antygomonas Nebelsick, 1990 (additional source)
Aphanipathes Brook, 1889 (additional source)
Aphanostoma Ørsted, 1845 (additional source)
Aphrodoctopus Roper & Mangold, 1991 accepted as Eledone Leach, 1817 (basis of record)
Apionsoma Sluiter, 1902 (additional source)
Aplidiopsis Lahille, 1890 (additional source)
Aptenodytes J. R. Forster, 1777 (additional source)
Arachnactis Sars, 1846 (additional source)
Arachnanthus Carlgren, 1912 (additional source)
Araneum Monniot C. & Monniot F., 1973 (additional source)
Archactinoposthia Dörjes, 1968 (additional source)
Archaphanostoma Dörjes, 1968 accepted as Baltalimania Ax, 1959 (additional source)
Archocelis Dörjes, 1968 (additional source)
Arctobdella de Silva & Kabata, 1961 accepted as Hemibdella van Beneden & Hesse, 1863. Revised (additional source)
Armadillogorgia Bayer, 1980 (additional source)
Armorhydra Swedmark & Teissier, 1958 (additional source)
Aschemonella Brady, 1879 (additional source)
Aselomaris Berrill, 1948 accepted as Rhizorhagium M. Sars, 1874 (additional source)
Astrangia Milne Edwards & Haime, 1848 (additional source)
Astromuricea Germanos, 1895 (additional source)
Astrorhiza Sandahl, 1858 (additional source)
Asymmetron Andrews, 1893 (basis of record)
Atolla Haeckel, 1880 (additional source)
Atorella Vanhöffen, 1902 (additional source)
Atriofronta Dörjes, 1968 (additional source)
Atriolum Kott, 1983 (basis of record)
Aulactinia Agassiz in Verrill, 1864 (additional source)
Aulocyathus Marenzeller, 1904 (additional source)