Abatus Troschel, 1851 (additional source)
Abyssaster Madsen, 1961 (additional source)
Abyssoclymene Hartman, 1967 (additional source)
Acanthephyra A. Milne-Edwards, 1881 (additional source)
Acanthistius Gill, 1862 (basis of record)
Acanthocope Beddard, 1885 (additional source)
Acanthocorbis S.Hara & E.Takahashi, 1984 (additional source)
Acanthoeca W.N.Ellis, 1930 (additional source)
Acanthoecopsis Norris, 1965 (additional source)
Acanthogorgia Gray, 1857 (additional source)
Acantholaimus Allgén, 1933 (additional source)
Acanthomunna Beddard, 1886 (additional source)
Acanthonotozomella Schellenberg, 1926 (additional source)
Acanthonotozomoides Schellenberg, 1931 (additional source)
Acanthonotozomopsis Watling & Holman, 1980 (additional source)
Acanthopharynx Marion, 1870 (additional source)
Acanthopriapulus van der Land, 1970 (additional source)
Acentrogobius Bleeker, 1874 (basis of record)
Achelia Hodge, 1864 (additional source)
Achoronemertes Crandall & Gibson, 1997 (basis of record)
Acineta Ehrenberg, 1834 (additional source)
Acryptolaria Norman, 1875 (additional source)
Actinernus Verrill, 1879 (additional source)
Actinocythereis Puri, 1953 † (additional source)
Actinonema Cobb, 1920 (additional source)
Actinoscyphia Stephenson, 1920 (additional source)
Actinostola Verrill, 1883 (additional source)
Actitis lliiger, 1811 (additional source)
Adagnesia Kott, 1963 (additional source)
Adelopora Cairns, 1982 (additional source)
Adercotryma Loeblich & Tappan, 1952 (additional source)
Adoncholaimus Filipjev, 1918 (additional source)
Aedicira Hartman, 1957 represented as Aricidea (Aedicira) Hartman, 1957 (additional source)
Aegaeon Agassiz, 1846 (additional source)
Aegialoalaimus de Man, 1907 (additional source)
Aeginura Haeckel, 1879 (additional source)
Aglaoprimnoa Bayer, 1996 (additional source)
Agnezia Monniot C. & Monniot F., 1991 (additional source)
Aimulosia Jullien, 1888 (additional source)
Alabaminella Saidova, 1975 (additional source)
Alaimella Cobb, 1920 (additional source)
Alcataenia Spasskaya, 1971 (additional source)
Algensiella Cottarelli & Baldari, 1987 (additional source)
Allantion Sandon, 1924 (additional source)
Allocyttus McCulloch, 1914 (additional source)
Alloeocarpa Michaelsen, 1900 (additional source)
Allogaussia Schellenberg, 1926 (additional source)
Allogromia Rhumbler, 1904 (additional source)
Allopora Ehrenberg, 1834 accepted as Stylaster Gray, 1831 (additional source)
Allorchestes Dana, 1849 (additional source)
Alopochelidon Ridgway, 1903 (additional source)
Altenaeum Spaink, 1972 (additional source)
Althoffia Lohmann, 1892 (additional source)
Alveolophragmium Shchedrina, 1936 (basis of record)
Amage Malmgren, 1866 (additional source)
Amalosoma Fisher, 1948 (additional source)
Amaryllis Haswell, 1879 (additional source)
Amathillopsis Heller, 1875 (additional source)
Ambassis Cuvier, 1828 (basis of record)
Amblyopsoides O.S. Tattersall, 1955 (additional source)
Ambunguipes Huys, 1990 (additional source)
Amigdoscalpellum Zevina, 1978 (additional source)
Ammobaculites Cushman, 1910 (additional source)
Ammoglobigerina Eimer & Fickert, 1899 (additional source)
Ammolagena Eimer & Fickert, 1899 (additional source)
Ammothea Leach, 1814 (additional source)
Amoeba Ehrenberg, 1830 (additional source)
Ampharana Hartman, 1967 (additional source)
Ampharetides Ehlers, 1913 accepted as Terebellides Sars, 1835 (additional source)
Amphicteis Grube, 1850 (additional source)
Amphidelus Thorne, 1939 (additional source)
Amphilochella Schellenberg, 1926 (additional source)
Amphimonhystera Allgén, 1929 (additional source)
Amphimonhystrella Timm, 1961 (additional source)
Amphiodia Verrill, 1899 (additional source)
Amphipneustes Koehler, 1900 (additional source)
Amphogona Browne, 1905 (additional source)
Amythas Benham, 1921 (additional source)
Ananthura Barnard, 1925 (additional source)
Anapta Semper, 1867 (additional source)
Anasterias Perrier, 1875 (additional source)
Anchiphimedia K.H. Barnard, 1930 (additional source)
Ancistrocheirus J. E. Gray, 1849 (additional source)
Ancistrosyllis McIntosh, 1878 (additional source)
Ancyromonas Kent, 1881 (additional source)
Andaniexis Stebbing, 1906 (additional source)
Andaniotes Stebbing, 1897 (additional source)
Andreella Jullien, 1888 (additional source)
Angulogerina Cushman, 1927 accepted as Trifarina Cushman, 1923 (additional source)
Anguloscalpellum Zevina, 1978 (additional source)
Anhinga Brisson, 1760 (additional source)
Anisometra John, 1939 (additional source)
Annatiara Russell, 1940 (additional source)
Anobothrella Hartman, 1967 accepted as Anobothrus Levinsen, 1884 (additional source)
Anobothrus Levinsen, 1884 (additional source)
Anomotaenia Cohn, 1900 (additional source)
Anophiura H.L. Clark, 1939 (additional source)
Anoplostoma Bütschli, 1874 (additional source)
Anotopterus Zugmayer, 1911 (additional source)
Anotylus Thomson, 1859 (additional source)

 authority

 for Hippomonavella Canu & Bassler in Bassler, 1934

Bassler, 1934 [details]