Acontiaria Stephenson, 1935 (basis of record)
Acthelmis intestinalis (Fabricius, 1780) (additional source)
Acthelmis schaudinnii Carlgren, 1921 accepted as Haliactis arctica Carlgren, 1921 (basis of record)
Actinauge abyssorum (Gravier, 1918) accepted as Actinauge karinae Fautin, 2016 (basis of record)
Actinauge abyssorum Carlgren, 1934 (additional source)
Actinauge cristata Riemann-Zürneck, 1986 (additional source)
Actinauge longicornis (Verrill, 1882) (basis of record)
Actinauge richardi (Marion, 1906) (additional source)
Actinauge rugosa Verrill, 1922 accepted as Hormathia nodosa (Fabricius, 1780) (source of synonymy)
Actinauge verrilli McMurrich, 1893 accepted as Actinauge verrillii McMurrich, 1893 (basis of record)
Actinauge verrillii McMurrich, 1893 (basis of record)
Actinernidae Stephenson, 1922 (additional source)
Actinernus michaelsarsi Carlgren, 1918 (additional source)
Actinernus nobilis Verrill, 1879 (basis of record)
Actinia candida Müller, 1776 accepted as Metridium senile (Linnaeus, 1761) (basis of record)
Actinia cari Delle Chiaje, 1822 (additional source)
Actinia elongata Delle Chiaje, 1825 (additional source)
Actinia equina (Linnaeus, 1758) (additional source)
Actinia equina mediterranea Schmidt, 1971 accepted as Actinia mediterranea Schmidt, 1971 (additional source)
Actinia filiformis Rapp, 1829 accepted as Cereus filiformis (Rapp, 1829) (additional source)
Actinia fragacea Tugwell, 1856 (additional source)
Actinia mediterranea Schmidt, 1971 (basis of record)
Actinia nitida Dawson, 1858 accepted as Stomphia coccinea (Müller, 1776) (basis of record)
Actinia obtruncata Stimpson, 1853 (additional source)
Actinia prasina Gosse, 1860 (additional source)
Actinia sali Monteiro, Sole-Cava & Thorpe, 1997 (basis of record)
Actinia schmidti Monteiro, Sole-Cava & Thorpe, 1997 accepted as Actinia mediterranea Schmidt, 1971 (basis of record)
Actinia sipunculoides Stimpson, 1853 accepted as Edwardsia sipunculoides (Stimpson, 1853) (source of synonymy)
Actinia striata Quoy & Gaimard, 1833 (additional source)
Actinia striata Rizzi, 1907 (additional source)
Actiniaria (additional source)
Actinioidea Rafinesque, 1815 (basis of record)
Actinoscyphia aurelia (Stephenson, 1918) (additional source)
Actinoscyphia saginata (Verrill, 1882) (additional source)
Actinostola abyssorum (Danielssen, 1890) (basis of record)
Actinostola callosa (Verrill, 1882) (additional source)
Actinostola spetsbergensis Carlgren, 1893 accepted as Glandulactis spetsbergensis (Carlgren, 1893) (basis of record)
Actinothoe clavata (Ilmoni, 1830) accepted as Sagartiogeton undatus (Müller, 1778) accepted as Cylista undata (Müller, 1778) accepted as Sagartia undata (Müller, 1778) (basis of record)
Actinothoe modesta (Verrill, 1866) (additional source)
Actinothoe sphyrodeta (Gosse, 1858) (additional source)
Adamsia carciniopados (Otto, 1823) accepted as Adamsia palliata (Fabricius, 1779) accepted as Calliactis palliata (Fabricius, 1779) (additional source)
Adamsia palliata (Bohadsch, 1761) accepted as Adamsia palliata (Fabricius, 1779) accepted as Calliactis palliata (Fabricius, 1779) (additional source)
Adamsia palliata (Fabricius, 1779) accepted as Calliactis palliata (Fabricius, 1779) (basis of record)
Adamsia sociabilis Verrill, 1882 (basis of record)
Aiptasia couchii Gosse (additional source)
Aiptasia diaphana (Rapp, 1829) accepted as Exaiptasia diaphana (Rapp, 1829) (additional source)
Aiptasia mutabilis (Gravenhorst, 1831) (additional source)
Aiptasiogeton hyalinus (Delle Chiaje, 1822) (additional source)
Aiptasiogeton pellucidus (Hollard, 1848) accepted as Aiptasiogeton hyalinus (Delle Chiaje, 1822) (additional source)
Alicia costae (Panceri, 1868) accepted as Alicia mirabilis Johnson, 1861 (basis of record)
Alicia mirabilis Johnson, 1861 (additional source)
Allantactis parasitica Danielssen, 1890 (additional source)
Amphianthus bathybium Hertwig, 1882 (additional source)
Amphianthus crassus (Gravier, 1918) accepted as Gliactis crassa Gravier, 1918 (source of synonymy)
Amphianthus dohrnii (Koch, 1878) (additional source)
Amphianthus impeditus (Gravier, 1918) accepted as Stephanauge impedita (Gravier, 1918) (source of synonymy)
Amphianthus ingolfi Carlgren, 1942 (additional source)
Amphianthus islandicus Carlgren, 1942 (additional source)
Amphianthus margaritaceus (Danielssen, 1890) (additional source)
Amphianthus michaelsarsi Carlgren, 1934 (additional source)
Amphianthus mirabilis (Verrill, 1879) (basis of record)
Amphianthus mopseae (Danielssen, 1890) (additional source)
Amphianthus norvegicus Carlgren, 1942 (additional source)
Amphianthus verruculatus Carlgren, 1942 (additional source)
Andresia partenopea (Andrès, 1883) (source of synonymy)
Andresia parthenopea (Andrès, 1883) accepted as Andresia partenopea (Andrès, 1883) (additional source)
Andvakia mirabilis Danielssen, 1890 (additional source)
Andvakia parva Carlgren, 1940 (additional source)
Anemonactis mazeli (Jourdan, 1880) (additional source)
Anemonia melanaster (Verrill, 1901) (additional source)
Anemonia rustica (additional source)
Anemonia sargassensis Hargitt, 1908 (additional source)
Anemonia sulcata (Pennant, 1777) (additional source)
Anemonia viridis (Forsskål, 1775) (additional source)
Antholoba achates (Drayton in Dana, 1846) (additional source)
Antholoba perdix (Verrill, 1882) (basis of record)
Anthopleura ballii (Cocks, 1851) (additional source)
Anthopleura biscayensis (Fischer, 1874) (source of synonymy)
Anthopleura crassa (Andrès, 1880) accepted as Cribrinopsis crassa (Andrès, 1881) (additional source)
Anthopleura rubripunctata (Grube, 1840) accepted as Bunodactis rubripunctata (Grube, 1840) (source of synonymy)
Anthopleura thallia (Gosse, 1854) (additional source)
Anthosactis ingolfi Carlgren, 1921 (additional source)
Anthosactis janmayeni Danielssen, 1890 (additional source)
Anthothoe affinis (Johnson, 1861) (basis of record)
Antipatharia (basis of record)
Antipathes (Cirripathes) setacea occidentalis Gray, 1860 accepted as Stichopathes occidentalis Gray, 1860 (basis of record)
Antipathes dissecta Duchassaing de Fombressin & Michelotti, 1864 (basis of record)
Antipathes setacea Gray, 1860 accepted as Stichopathes setacea (Gray, 1860) (basis of record)
Antipathidae Ehrenberg, 1834 (additional source)
Arachnactidae McMurrich, 1910 (additional source)
Arachnactis Sars, 1846 (additional source)
Arachnactis albida Sars, 1846 (additional source)
Arachnactis bournei Fowler, 1897 accepted as Cerianthus lloydii Gosse, 1859 accepted as Synarachnactis lloydii (Gosse, 1859) (basis of record)
Arachnactis lloydii (Gosse, 1859) accepted as Cerianthus lloydii Gosse, 1859 accepted as Synarachnactis lloydii (Gosse, 1859) (basis of record)
Athenaria (basis of record)
Aulactinia spetsbergensis (Carlgren, 1921) (additional source)
Aulactinia stella (Verrill, 1864) (additional source)
Aulactinia verrucosa (Pennant, 1777) accepted as Bunodactis verrucosa (Pennant, 1777) (additional source)
Aureliania Gosse, 1860 (basis of record)
Aureliania heterocera (Thompson, 1853) accepted as Capnea sanguinea Forbes, 1841 (basis of record)

Madeira for Sagartia affinis Johnson, 1861