• Abyssinoe scopa [auct. lapsus] accepted as Abyssoninoe scopa (Fauchald, 1974)
• Abyssoninoe abyssorum (McIntosh, 1885)
• Abyssoninoe bidentata D'Alessandro, Cosentino, Giacobbe, Andaloro & Romeo, 2014
• Abyssoninoe galatheae (Knox & Green, 1972)
• Abyssoninoe hibernica (McIntosh, 1903)
• Abyssoninoe orensanzi Hartmann-Schröder & Rosenfeldt, 1992
• Abyssoninoe phuketensis Oug, 2002
• Abyssoninoe scopa (Fauchald, 1974)
• Abyssoninoe scopa aequilobata (Winsnes, 1981) accepted as Abyssoninoe hibernica (McIntosh, 1903)
• Abyssoninoe winsnesae Frame, 1992
• Aciculomarphysa comes Hartmann-Schröder in Hartmann-Schröder & Zibrowius, 1998
• Aenone lithophaga Risso, 1826
• Aglaura fulgida Lamarck, 1818 accepted as Oenone fulgida (Lamarck, 1818)
• Aglaurides erythraeensis Gravier, 1900 accepted as Oenone fulgida (Lamarck, 1818)
• Aglaurides erythraeensis symmetrica Fauvel, 1914 accepted as Oenone fulgida (Lamarck, 1818)
• Aglaurides fulgida (Savigny in Lamarck, 1818) accepted as Oenone fulgida (Lamarck, 1818)
• Americonuphis casamiquelorum Orensanz, 1974 accepted as Australonuphis casamiquelorum (Orensanz, 1974)
• Americonuphis magna (Andrews, 1891)
• Americonuphis reesei Fauchald, 1973
• Amphiro atlantica Kinberg, 1865 accepted as Marphysa atlantica (Kinberg, 1865)
• Amphiro johnsoni Langerhans, 1880 accepted as Marphysa johnsoni (Langerhans, 1880)
• Amphiro pacifica Rullier, 1972 accepted as Marphysa pacifica (Rullier, 1972)
• Amphiro simplex Langerhans, 1884 accepted as Marphysa simplex (Langerhans, 1884)
• Anchidorvillea moniliformis Hilbig & Blake, 1991
• Anchinothria abranchiata (McIntosh, 1885) accepted as Anchinothria pycnobranchiata (McIntosh, 1885)
• Anchinothria cirrobranchiata (Moore, 1903)
• Anchinothria cobra (Chamberlin, 1919)
• Anchinothria crassisetosa (Chamberlin, 1919)
• Anchinothria fissurata (Fauchald, 1972)
• Anchinothria glutinatrix (Ehlers, 1887)
• Anchinothria hiatidentata (Moore, 1911)
• Anchinothria macrobranchiata (McIntosh, 1885)
• Anchinothria parvula Budaeva & Paxton, 2013
• Anchinothria pourtalesii (Ehlers, 1887)
• Anchinothria pycnobranchiata (McIntosh, 1885)
• Anchinothria sombreriana (McIntosh, 1885)
• Anchinothria tosaensis Imajima, 1999
• Andiprion paxtonae Hints, Tonarová, Eriksson, Rubinstein & De la Puente, 2017 †
• Andromache diphyllidia (Schmarda, 1861) accepted as Oenone fulgida (Lamarck, 1818)
• Anisoceras bioculata Grube, 1856 accepted as Dorvillea bioculata (Grube, 1856)
• Anisoceras rubra Grube, 1856 accepted as Dorvillea rubra (Grube, 1856)
• Anisoceras vittata Grube, 1856 accepted as Dorvillea vittata (Grube, 1856)
• Aotearia sulcaticeps Benham, 1927 (uncertain > taxon inquirendum)
• Apodotrocha progenerans Westheide & Riser, 1983
• Aponuphis annae Paxton, 2017
• Aponuphis bellani Paxton, 2017
• Aponuphis bilineata (Baird, 1870)
• Aponuphis bilineata grubii (Marenzeller, 1886) accepted as Aponuphis grubii (Marenzeller, 1886)
• Aponuphis brementi (Fauvel, 1916)
• Aponuphis chistikovi Detinova, 1986
• Aponuphis danicae Paxton, 2017
• Aponuphis fauveli (Rioja, 1918) accepted as Aponuphis brementi (Fauvel, 1916)
• Aponuphis grubii (Marenzeller, 1886)
• Aponuphis ornata (Fauvel, 1928)
• Aponuphis rigida (Claparède, 1868)
• Aponuphis rubra (Langerhans, 1880) accepted as Aponuphis bilineata (Baird, 1870)
• Aponuphis willsiei Cantone & Bellan, 1996
• Aponuphis willsii [auct.] accepted as Aponuphis willsiei Cantone & Bellan, 1996
• Apophryotrocha mutabiliseta Jumars, 1974
• Arabella (Arabella) iricolor (Montagu, 1804) accepted as Arabella iricolor (Montagu, 1804)
• Arabella (Arabella) pectinata Fauchald, 1970 accepted as Arabella pectinata Fauchald, 1970
• Arabella (Arabella) protomutans Orensanz, 1990 accepted as Arabella protomutans Orensanz, 1990
• Arabella (Arabella) pulvinata Zanol & Ruta, 2015
• Arabella (Arabella) semimaculata (Moore, 1911) accepted as Arabella semimaculata (Moore, 1911)
• Arabella (Cenothrix) mutans (Chamberlin, 1919)
• Arabella (Cenothrix) robusta Zanol & Ruta, 2015
• Arabella aracaensis Steiner & Amaral, 2009
• Arabella atlantica Crossland, 1924
• Arabella attenuata Treadwell, 1906 accepted as Notocirrus attenuatus (Treadwell, 1906)
• Arabella cincta Hartmann-Schröder, 1962
• Arabella coeca Fauvel, 1940
• Arabella debilis
• Arabella debilis maorica (Augener, 1924) accepted as Drilonereis maorica (Augener, 1924)
• Arabella diversimaxillata Szaniawski & Gazdzicki, 1978 †
• Arabella dubia Hansen, 1882 accepted as Lumbrineris janeirensis Augener, 1934
• Arabella endonata Emerson, 1974
• Arabella geniculata (Claparède, 1868)
• Arabella iricolor (Montagu, 1804)
• Arabella iricolor caerulea (Schmarda, 1861)
• Arabella iricolor iricolor (Montagu, 1804)
• Arabella iridescens Treadwell, 1906
• Arabella lagunae Chamberlin, 1919 accepted as Arabella iricolor (Montagu, 1804)
• Arabella logani Crossland, 1924
• Arabella longicirrata Hartmann-Schröder, 1979
• Arabella longipedata Monro, 1931
• Arabella maculata (Milne Edwards, 1836) accepted as Arabella iricolor (Montagu, 1804)
• Arabella maculifera (Grube, 1878)
• Arabella maculosa Verrill, 1900 accepted as Arabella iricolor (Montagu, 1804)
• Arabella mimetica Chamberlin, 1919
• Arabella monroi Colbath, 1989
• Arabella multidentata (Ehlers, 1887) accepted as Arabella iricolor (Montagu, 1804)
• Arabella munda Chamberlin, 1918 accepted as Arabella semimaculata (Moore, 1911)
• Arabella mutans (Chamberlin, 1919)
• Arabella nesidensis (Delle Chiaje, 1828)
• Arabella novecrinita Crossland, 1924 accepted as Arabella mutans (Chamberlin, 1919)
• Arabella novecrinita asymmetrica Crossland, 1924 accepted as Arabella atlantica Crossland, 1924
• Arabella novecrinita atlantica Crossland, 1924 accepted as Arabella atlantica Crossland, 1924
• Arabella novecrinita logani Crossland, 1924 accepted as Arabella logani Crossland, 1924
• Arabella pacifica Treadwell, 1941 accepted as Arabella semimaculata (Moore, 1911)
• Arabella panamensis Colbath, 1989