Abietinaria Kirchenpauer, 1884 (additional source)
Abylopsis tetragona (Otto, 1823) (additional source)
Acanthella Schmidt, 1862 (additional source)
Acanthephyra purpurea A. Milne-Edwards, 1881 (additional source)
Acanthochondrites annulatus (Olsson, 1869) (additional source)
Acanthogorgia armata Verrill, 1878 (additional source)
Acanthoscina acanthodes (Stebbing, 1895) (additional source)
Acartia (Acartia) danae Giesbrecht, 1889 (basis of record)
Acartia (Acartia) negligens Dana, 1849 (basis of record)
Acartia (Acartiura) longiremis (Lilljeborg, 1853) (basis of record)
Acasta spongites (Poli, 1791) (additional source)
Acervulina inhaerens Schultze, 1854 (additional source)
Achnanthes longipes C.Agardh, 1824 (additional source)
Acinetospora crinita (Carmichael) Sauvageau, 1899 (additional source)
Acrochaetium densum (K.M.Drew) Papenfuss, 1945 accepted as Acrochaetium catenulatum M.Howe, 1914 (additional source)
Acrochaetium humile (Rosenvinge) Børgesen, 1915 (additional source)
Acrochaetium microscopicum (Nägeli ex Kützing) Nägeli, 1858 (additional source)
Acrochaetium parvulum (Kylin) Hoyt, 1920 (additional source)
Acrosorium venulosum (Zanardini) Kylin, 1924 (additional source)
Actinocyclus curvatulus Janisch, 1874 (additional source)
Actinocyclus normanii (Gregory) Hustedt, 1957 (additional source)
Actinocyclus subtilis (W.Gregory) Ralfs, 1861 (additional source)
Actinonema pachydermatum Cobb, 1920 (additional source)
Actinoptychus splendens (Shadbolt) Ralfs ex Pritchard, 1861 (additional source)
Actitis hypoleucos (Linnaeus, 1758) (additional source)
Adna anglica (Sowerby, 1823) (basis of record)
Aegaeon lacazei (Gourret, 1887) (additional source)
Aegina citrea Eschscholtz, 1829 (additional source)
Aeginura grimaldii Maas, 1904 (additional source)
Aegisthus mucronatus Giesbrecht, 1891 (additional source)
Aeolidiella Bergh, 1867 (additional source)
Aequorea macrodactyla (Brandt, 1835) (additional source)
Aequorea pensilis (Haeckel, 1879) (additional source)
Aetea anguina (Linnaeus, 1758) (additional source)
Aetea truncata (Landsborough, 1852) (additional source)
Aetideopsis armata (Boeck, 1872) (additional source)
Aetideopsis multiserrata (Wolfenden, 1904) (additional source)
Aetideus armatus (Boeck, 1872) (additional source)
Aetideus giesbrechti Cleve, 1904 (additional source)
Agalma elegans (M. Sars, 1846) (additional source)
Aglaophenia Lamouroux, 1812 (additional source)
Aglaophenia parvula Bale, 1882 (additional source)
Aglaophenia tubulifera (Hincks, 1861) (additional source)
Aix galericulata (Linnaeus, 1758) (additional source)
Akashiwo sanguinea (K.Hirasaka) Gert Hansen & Moestrup, 2000 (additional source)
Alciopina parasitica Claparède & Panceri, 1867 (additional source)
Alcyonidium mytili Dalyell, 1848 accepted as Alcyonidioides mytili (Dalyell, 1848) (additional source)
Alderia modesta (Lovén, 1844) (additional source)
Alepisaurus ferox Lowe, 1833 (additional source)
Alexandrium catenella (Whedon & Kofoid) Balech, 1985 (additional source)
Alopias superciliosus Lowe, 1841 (additional source)
Alopias vulpinus (Bonnaterre, 1788) (additional source)
Amaeana trilobata (Sars, 1863) (additional source)
Amallothrix arcuata (Sars G.O., 1920) (additional source)
Amallothrix gracilis (Sars G.O., 1905) (additional source)
Ameira longipes Boeck, 1865 (additional source)
Ammolagena clavata (Jones & Parker, 1860) (additional source)
Ammonia beccarii (Linnaeus, 1758) (additional source)
Ammothea hilgendorfi (Böhm, 1879) (additional source)
Ampelisca brevicornis (A. Costa, 1853) (additional source)
Ampharete acutifrons (Grube, 1860) (additional source)
Ampharete arctica Malmgren, 1866 accepted as Ampharete finmarchica (M. Sars, 1865) (additional source)
Amphibalanus amphitrite (Darwin, 1854) (additional source)
Amphibalanus eburneus (Gould, 1841) (additional source)
Amphibalanus improvisus (Darwin, 1854) (additional source)
Amphibalanus reticulatus (Utinomi, 1967) (additional source)
Amphicaryon acaule Chun, 1888 (additional source)
Amphicteis gunneri (M. Sars, 1835) (additional source)
Amphidinium carterae Hulburt, 1957 (additional source)
Amphilectus fucorum (Esper, 1794) (additional source)
Amphilochus spencebatei (Stebbing, 1876) accepted as Apolochus spencebatei (Stebbing, 1876) (additional source)
Amphinema dinema (Péron & Lesueur, 1810) (additional source)
Amphinema rugosum (Mayer, 1900) (additional source)
Amphipholis squamata (Delle Chiaje, 1828) (additional source)
Amphitrite cirrata Müller, 1776 (additional source)
Ampithoe ramondi Audouin, 1826 (additional source)
Ampithoe valida S.I. Smith, 1873 (additional source)
Amygdalum peasei (Newcomb, 1870) (additional source)
Anas acuta Linnaeus, 1758 (additional source)
Anas clypeata Linnaeus, 1758 accepted as Spatula clypeata (Linnaeus, 1758) (additional source)
Anas crecca Linnaeus, 1758 (additional source)
Anas formosa Georgi, 1775 (additional source)
Anas penelope Linnaeus, 1758 accepted as Mareca penelope (Linnaeus, 1758) (additional source)
Anas platyrhynchos Linnaeus, 1758 (additional source)
Anas querquedula Linnaeus, 1758 accepted as Spatula querquedula (Linnaeus, 1758) (additional source)
Anas strepera Linnaeus, 1758 (additional source)
Anchylomera blossevillei H. Milne Edwards, 1830 (additional source)
Ancistrosyllis groenlandica McIntosh, 1878 (additional source)
Annatiara affinis (Hartlaub, 1914) (additional source)
Anomocora Studer, 1878 (additional source)
Anonyx lilljeborgii Boeck, 1871 accepted as Anonyx lilljeborgi Boeck, 1871 (additional source)
Anoplostoma viviparum (Bastian, 1865) Bütschli, 1874 (additional source)
Anser albifrons (Scopoli, 1769) (additional source)
Anser anser (Linnaeus, 1758) (additional source)
Anser erythropus (Linnaeus, 1758) (additional source)
Anser fabalis (Latham, 1787) (additional source)
Antennella Allman, 1877 (additional source)
Antennella secundaria (Gmelin, 1791) (additional source)
Anthomastus Verrill, 1878 (additional source)
Antipathes Pallas, 1766 (additional source)