Abarenicola Wells, 1959 (basis of record)
Abarenicola claparedei (Levinsen, 1884) accepted as Abarenicola claparedi (Levinsen, 1884) (basis of record)
Abyssoninoe Orensanz, 1990 (additional source)
Acanthicolepis McIntosh, 1900 (additional source)
Acanthicolepis asperrima (M. Sars, 1861) (additional source)
Acholoe Claparède, 1870 (additional source)
Acholoe astericola (Delle Chiaje, 1841) accepted as Acholoe squamosa (Delle Chiaje, 1827) (additional source)
Acrocirrus Grube, 1873 (basis of record)
Acrocirrus frontifilis (Grube, 1860) (basis of record)
Aglaophamus agilis (Langerhans, 1880) (basis of record)
Aglaophamus malmgreni (Théel, 1879) (basis of record)
Aglaophamus rubella (Michaelsen, 1897) accepted as Aglaophamus agilis (Langerhans, 1880) (basis of record)
Alciopa Audouin & Milne Edwards, 1833 (additional source)
Alciopa reynaudii Audouin & H Milne Edwards, 1833 (additional source)
Alciopina Claparède & Panceri, 1867 (additional source)
Alciopina parasitica Claparède & Panceri, 1867 (additional source)
Alkmaria Horst, 1919 (basis of record)
Alkmaria romijni Horst, 1919 (additional source)
Amaeana Hartman, 1959 (additional source)
Amaeana trilobata (Sars, 1863) (additional source)
Amage Malmgren, 1866 (additional source)
Amage adspersa (Grube, 1863) (additional source)
Amage auricula Malmgren, 1866 (basis of record)
Amage scotica Clark, 1952 (basis of record)
Amblyosyllis Grube, 1857 (basis of record)
Amblyosyllis formosa (Claparède, 1863) accepted as Amblyosyllis spectabilis (Johnston in Baird, 1861) (basis of record)
Amblyosyllis madeirensis Langerhans, 1879 (basis of record)
Ampharete Malmgren, 1866 (additional source)
Ampharete acutifrons (Grube, 1860) (additional source)
Ampharete baltica Eliason, 1955 (additional source)
Ampharete falcata Eliason, 1955 (basis of record)
Ampharete finmarchica (M. Sars, 1865) (basis of record)
Ampharete goesi Malmgren, 1866 (basis of record)
Ampharete lindstroemi Hessle, 1917 (basis of record)
Ampharete petersenae Jirkov, 1997 (basis of record)
Ampharete vega (Wirén, 1883) (basis of record)
Amphicteis Grube, 1850 (additional source)
Amphicteis gunneri (M. Sars, 1835) (additional source)
Amphicteis midas (Gosse, 1855) (additional source)
Amphicteis sundevalli Malmgren, 1866 (basis of record)
Amphiduros Hartman, 1959 (basis of record)
Amphiduros fuscescens (Marenzeller, 1875) (additional source)
Amphiglena Claparède, 1864 (additional source)
Amphiglena mediterranea (Leydig, 1851) (basis of record)
Amphitrite Müller, 1771 (additional source)
Amphitrite cirrata Müller, 1776 (basis of record)
Amphitritides gracilis (Grube, 1860) (additional source)
Amythasides Eliason, 1955 (additional source)
Amythasides macroglossus Eliason, 1955 (basis of record)
Ancistrosyllis McIntosh, 1878 (additional source)
Ancistrosyllis groenlandica McIntosh, 1878 (basis of record)
Anobothrus Levinsen, 1884 (additional source)
Anobothrus gracilis (Malmgren, 1866) (additional source)
Aonides Claparède, 1864 (additional source)
Aonides oxycephala (Sars, 1862) (basis of record)
Aonides paucibranchiata Southern, 1914 (basis of record)
Aphelochaeta Blake, 1991 (additional source)
Aphelochaeta filiformis (Keferstein, 1862) (basis of record)
Aphelochaeta marioni (Saint-Joseph, 1894) (basis of record)
Aphelochaeta mcintoshi (Southern, 1914) (basis of record)
Aphelochaeta vivipara (Christie, 1984) accepted as Chaetozone vivipara (Christie, 1984) (basis of record)
Apistobranchus Levinsen, 1884 (additional source)
Apistobranchus tenuis Orrhage, 1962 (basis of record)
Apistobranchus tullbergi (Théel, 1879) (additional source)
Apomatus Philippi, 1844 (basis of record)
Apomatus similis Marion & Bobretzky, 1875 (basis of record)
Aponuphis Kucheruk, 1978 (additional source)
Aponuphis bilineata (Baird, 1870) (additional source)
Aponuphis brementi (Fauvel, 1916) (additional source)
Apoprionospio Foster, 1969 (additional source)
Arabella geniculata (Claparède, 1868) (basis of record)
Arabella iricolor (Montagu, 1804) (basis of record)
Arenicola Lamarck, 1801 (additional source)
Arenicola defodiens Cadman & Nelson-Smith, 1993 (additional source)
Arenicola marina (Linnaeus, 1758) (basis of record)
Arenicolides Mesnil, 1898 (additional source)
Arenicolides branchialis (Audouin & Milne Edwards, 1833) (basis of record)
Arenicolides ecaudata (Johnston, 1835) (basis of record)
Arenicolides grubii Claparède, 1868 (basis of record)
Arenotrocha Westheide & von Nordheim, 1985 (additional source)
Arenotrocha minuta (Lévi, 1954) (additional source)
Aricidea Webster, 1879 (additional source)
Aricidea abranchiata Hartman, 1965 (basis of record)
Aricidea albatrossae Pettibone, 1957 represented as Aricidea (Aricidea) albatrossae Pettibone, 1957 (basis of record)
Aricidea capensis Day, 1961 represented as Aricidea (Aricidea) capensis Day, 1961 (basis of record)
Aricidea capensis bansei Laubier & Ramos, 1974 accepted as Aricidea (Aricidea) bansei Laubier & Ramos, 1974 (basis of record)
Aricidea catherinae Laubier, 1967 represented as Aricidea (Acmira) catherinae Laubier, 1967 (basis of record)
Aricidea cerrutii Laubier, 1966 represented as Aricidea (Acmira) cerrutii Laubier, 1966 (basis of record)
Aricidea claudiae Laubier, 1967 represented as Aricidea (Strelzovia) claudiae Laubier, 1967 (basis of record)
Aricidea fragilis Webster, 1879 represented as Aricidea (Aricidea) fragilis Webster, 1879 (basis of record)
Aricidea laubieri Hartley, 1981 represented as Aricidea (Acmira) laubieri Hartley, 1981 (basis of record)
Aricidea minuta Southward, 1956 represented as Aricidea (Aricidea) minuta Southward, 1956 (basis of record)
Aricidea philbinae Brown, 1976 represented as Aricidea (Acmira) philbinae Brown, 1976 (basis of record)
Aricidea quadrilobata Webster & Benedict, 1887 represented as Aricidea (Strelzovia) quadrilobata Webster & Benedict, 1887 (basis of record)
Aricidea roberti Hartley, 1983 represented as Aricidea (Strelzovia) roberti Hartley, 1984 (basis of record)
Aricidea simonae Laubier & Ramos, 1974 represented as Aricidea (Acmira) simonae Laubier & Ramos, 1974 (basis of record)
Aricidea suecica Eliason, 1920 represented as Aricidea (Strelzovia) suecica Eliason, 1920 (additional source)
Aricidea wassi Pettibone, 1965 represented as Aricidea (Aricidea) wassi Pettibone, 1965 (basis of record)
Armandia Filippi, 1861 (additional source)
Armandia cirrhosa Filippi, 1861 (basis of record)