Acontiaria Stephenson, 1935 (basis of record)
Actinauge abyssorum (Gravier, 1918) accepted as Actinauge karinae Fautin, 2016 (basis of record)
Actinauge abyssorum Carlgren, 1934 (additional source)
Actinauge bocki Carlgren, 1943 (additional source)
Actinauge granulata Carlgren, 1928 (additional source)
Actinauge longicornis (Verrill, 1882) (basis of record)
Actinauge longicornis var. caribaea Verrill, 1883 accepted as Actinauge longicornis (Verrill, 1882) (basis of record)
Actinauge nexilis Verrill, 1883 accepted as Stephanauge nexilis (Verrill, 1883) (basis of record)
Actinauge nodosa Fabricius, 1780 accepted as Hormathia nodosa (Fabricius, 1780) (basis of record)
Actinauge nodosa var. coronata Verrill, 1883 accepted as Chondrophellia coronata (Verrill, 1883) (basis of record)
Actinauge nodosa var. tuberculosa Verrill, 1883 accepted as Actinauge verrillii McMurrich, 1893 (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)
Actinecta de Blainville, 1830 (basis of record)
Actinecta olivacea (Le Sueur, 1817) (basis of record)
Actinernidae Stephenson, 1922 (additional source)
Actinernus antarcticus (Carlgren, 1914) (basis of record)
Actinernus aurelia Stephenson, 1918 accepted as Actinoscyphia aurelia (Stephenson, 1918) (basis of record)
Actinernus elongatus (Hertwig, 1882) (additional source)
Actinernus michaelsarsi Carlgren, 1918 (additional source)
Actinernus nobilis Verrill, 1879 (basis of record)
Actinernus plebeius McMurrich, 1893 accepted as Actinoscyphia plebeia (McMurrich, 1893) (basis of record)
Actinernus robustus (Hertwig, 1882) (additional source)
Actinernus saginatus Verrill, 1882 accepted as Actinoscyphia saginata (Verrill, 1882) (basis of record)
Actinia abyssicola Moseley, 1877 accepted as Stephanauge abyssicola (Moseley, 1877) (basis of record)
Actinia adspersa Gravenhorst, 1831 accepted as Actinia cari Delle Chiaje, 1822 (basis of record)
Actinia cari Delle Chiaje, 1822 (additional source)
Actinia clavata Ilmoni, 1830 accepted as Sagartiogeton undatus (Müller, 1778) accepted as Cylista undata (Müller, 1778) accepted as Sagartia undata (Müller, 1778) (basis of record)
Actinia iris Müller, 1789 (additional source)
Actinia plumosa accepted as Metridium dianthus (Ellis, 1768) (basis of record)
Actinia undata Ilmoni, 1830 accepted as 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)
Actiniaria (additional source)
Actinioidea Rafinesque, 1815 (basis of record)
Actinoscyphia aurelia (Stephenson, 1918) (additional source)
Actinoscyphia groendyki Eash-Loucks & Fautin, 2012 (basis of record)
Actinoscyphia plebeia (McMurrich, 1893) (additional source)
Actinoscyphia saginata (Verrill, 1882) (additional source)
Actinoscyphia verrilli (Gravier, 1918) (additional source)
Actinostola abyssorum (Danielssen, 1890) (basis of record)
Actinostola atrostoma Stephenson, 1918 accepted as Actinostola callosa (Verrill, 1882) (basis of record)
Actinostola bulbosa (Carlgren, 1928) (basis of record)
Actinostola callosa (Verrill, 1882) (additional source)
Actinostola capensis (Carlgren, 1928) (basis of record)
Actinostola crassicornis (Hertwig, 1882) (additional source)
Actinostola excelsa McMurrich, 1823 accepted as Actinostola crassicornis (Hertwig, 1882) (additional source)
Actinostola faeculenta (McMurrich, 1893) (basis of record)
Actinostola georgiana Carlgren, 1927 (additional source)
Actinostola intermedia Carlgren, 1899 accepted as Actinostola crassicornis (Hertwig, 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)
Adamsia involvens McMurrich, 1893 accepted as Paracalliactis consors (Verrill, 1882) (basis of record)
Adamsia obvolva Daly, Ardelean, Cha, Campbell & Fautin, 2004 accepted as Paracalliactis obvolva (Daly, Ardelean, Cha, Campbell & Fautin, 2004) (additional source)
Adamsia palliata (Fabricius, 1779) accepted as Calliactis palliata (Müller, 1776) (basis of record)
Adamsia sociabilis Verrill, 1882 accepted as Calliactis sociabilis (Verrill, 1882) (basis of record)
Aegir (basis of record)
Aegir frigidus Danielssen, 1887 accepted as Halcampoides purpureus (Studer, 1879) (basis of record)
Allantactis parasitica Danielssen, 1890 (additional source)
Alvinactis Rodríguez, Castorani & Daly, 2008 (basis of record)
Alvinactis chessi Zelnio, Rodríguez & Daly, 2009 (basis of record)
Alvinactis reu Rodríguez, Castorani & Daly, 2008 (basis of record)
Amphianthus (Korenia) (basis of record)
Amphianthus (Korenia) radiatus Carlgren, 1928 accepted as Amphianthus radiatus Carlgren, 1928 (basis of record)
Amphianthus bathybium Hertwig, 1882 (additional source)
Amphianthus ingolfi Carlgren, 1942 (additional source)
Amphianthus lacteus (Mc Murrich, 1893) (additional source)
Amphianthus margaritaceus (Danielssen, 1890) (additional source)
Amphianthus michaelsarsi Carlgren, 1934 (additional source)
Amphianthus minutus (Hertwig, 1882) (additional source)
Amphianthus mirabilis (Verrill, 1879) (basis of record)
Amphianthus mopseae (Danielssen, 1890) (additional source)
Amphianthus ornatum Hertwig, 1888 accepted as Amphianthus bathybium Hertwig, 1882 (basis of record)
Amphianthus ornatus Hertwig, 1888 accepted as Amphianthus bathybium Hertwig, 1882 (source of synonymy)
Amphianthus radiatus Carlgren, 1928 (additional source)
Amphianthus verruculatus Carlgren, 1942 (additional source)
Amphihelia Milne Edwards & Haime, 1849 accepted as Madrepora Linnaeus, 1758 (basis of record)
Anactinia pelagica Annandale, 1909 (additional source)
Anemonactis clavus (Quoy & Gaimard, 1833) (additional source)
Anemonactis mazeli (Jourdan, 1880) (additional source)
Angianthula Leloup, 1964 (basis of record)
Angianthula cerfontaini Leloup, 1968 (basis of record)
Antheomorphe (basis of record)
Antheomorphe elegans Hertwig, 1882 (basis of record)
Antheomorphidae Hertwig, 1882 (basis of record)
Anthoactis Leloup, 1932 (basis of record)
Anthoactis armauer-hanseni Leloup, 1932 accepted as Anthoactis armauerhanseni Leloup, 1932 (source of synonymy)
Antholoba achates (Drayton in Dana, 1846) (additional source)
Anthopleura anjunae Den Hartog & Vennam, 1993 (additional source)
Anthopleura fuscoviridis Carlgren, 1949 (source of synonymy)
Anthopleura midori Uchida & Muramatsu, 1958 accepted as Anthopleura fuscoviridis Carlgren, 1949 (additional source)
Anthosactis excavata (Hertwig, 1882) (additional source)
Anthosactis ingolfi Carlgren, 1921 (additional source)
Anthosactis jan mayeni accepted as Anthosactis janmayeni Danielssen, 1890 (basis of record)
Anthosactis janmayeni Danielssen, 1890 (additional source)
Anthosactis nomados White, Wakefield Pagels & Fautin, 1999 (additional source)
Anthosactis pearseae Daly & Gusmão, 2007 accepted as Ostiactis pearseae (Daly & Gusmão, 2007) (additional source)
Antipatharia (basis of record)
Antipathes (Cirripathes) desbonni (Duchassaing & Michelotti, 1864) accepted as Allopathes desbonni (Duchassaing & Michelotti, 1864) (basis of record)
Antipathes dissecta Duchassaing de Fombressin & Michelotti, 1864 (basis of record)

 Homonymy

 for Actinia striata Quoy & Gaimard, 1833

Junior primary homonym of *Actinia striata* Risso, 1826 (type of *Paractinia*) [details]

 Homonymy

 for Actinia striata Rizzi, 1907

Junior primary homonym of *Actinia striata* Risso, 1826 (type of *Paractinia*), and of Quoy and Gaimard, 1833 [details]

 Synonymy

 for Anemonia melanaster (Verrill, 1901)

Status of the species needs investigation [details]

 Taxonomy

 for Corynactis albida Agassiz, 1859

This is not considered a valid species. The name has been applied to two species: Haloclava producta (Stimpson, ... [details]

 Validity

 for Boloceroides hermaphroditica Carlgren, 1900

Possible synonym of Bolocera mcmurrichi. [details]

 Validity

 for Edwardsioides mamillata (Bourne, 1916)

nomen dubium according to Williams, 1981 [details]

 Validity

 for Euphellia cinclidifera Pax, 1908

Also treated as a synonym of Telmatactis cricoides (Duchassaing, 1850). [details]