• [non-Uristidae] albinus (K.H. Barnard, 1932)
• [non-Uristidae] dawsoni Hurley, 1963
• [non-Uristidae] georgianus (Schellenberg, 1931)
• [non-Uristidae] natalensis K.H. Barnard, 1916
• Aahithis erraticus (Schallreuter, 1985) †
• Aaptolasma americanum (Pilsbry, 1916) accepted as Hexelasma americanum Pilsbry, 1916
• Aaptolasma arafurae (Hoek, 1883) accepted as Hexelasma arafurae Hoek, 1913
• Aaptolasma brintoni Newman & Ross, 1971 accepted as Hexelasma brintoni (Newman & Ross, 1971)
• Aaptolasma callistoderma (Pilsbry, 1911) accepted as Hexelasma callistoderma Pilsbry, 1911
• Aaptolasma ecaudatum (Hiro, 1933) accepted as Pachylasma ecaudatum Hiro, 1939
• Aaptolasma fosteri (Newman & Ross, 1971) accepted as Mesolasma fosteri (Newman & Ross, 1981)
• Aaptolasma leptoderma Newman & Ross, 1971 accepted as Hexelasma leptoderma (Newman & Ross, 1971)
• Aaptolasma nolearia Foster, 1978 accepted as Hexelasma nolearia Foster, 1978
• Aaptolasma triderma Newman & Ross, 1971 accepted as Hexelasma triderma (Newman & Ross, 1971)
• Aatolana rapax Bruce, 1993
• Aatolana schioedtei (Miers, 1884)
• Aatolana springthorpei Keable, 1998
• Abacola holothuriae Edwards, 1891 accepted as Metis holothuriae (Edwards, 1891)
• Abasia inflata Cressey & Cressey, 1979
• Abasia pillaii Cressey & Cressey, 1979
• Abasia platyrostris Pillai, 1963
• Abasia pseudorostris Wilson C.B., 1908
• Abasia pusilla Cressey & Cressey, 1979
• Abasia tripartita (Shiino, 1955)
• Abatetia robusta (Parent, 1933)
• Abathescalpellum fissum (Hoek, 1907)
• Abathescalpellum koreanum (Hiro, 1933)
• Abdia latipalpus (Walker & Scott, 1903)
• Abdiacyclops cirratus Karanovic, 2005
• Abditacythere subterranea Hartmann, 1964
• Abebaioscia troglodytes Vandel, 1973
• Abergasilus amplexus Hewitt, 1978
• Aberomysis muranoi Bacescu & Iliffe, 1986
• Aberratylus aberrantis (J.L. Barnard, 1962)
• Aberroconcha plicata Adamczak, 1961 † accepted as  †
• Abgrallaspis cyanophylli (Signoret, 1869)
• Ablabesmyia mala (Hutton, 1902)
• Abludogammarus flavus (Dybowsky, 1874)
• Abludomelita aculeata (Chevreux, 1911)
• Abludomelita amoena (Hansen, 1888)
• Abludomelita breviarticulata (Ren, 2012)
• Abludomelita californica Alderman, 1936 accepted as Desdimelita californica (Alderman, 1936)
• Abludomelita denticulata (Nagata, 1965)
• Abludomelita gladiosa (Spence Bate, 1862)
• Abludomelita huanghaiensis (Ren, 2012)
• Abludomelita japonica (Nagata, 1965)
• Abludomelita klitinii Labay, 2016
• Abludomelita machaera (K.H. Barnard, 1955)
• Abludomelita mucronata (Griffiths, 1975)
• Abludomelita obtusata (Montagu, 1813)
• Abludomelita okhotensis Labay, 2016
• Abludomelita richardi (Chevreux, 1900)
• Abludomelita rotundactyla (Ren, 2012)
• Abludomelita semipalmata G. Karaman, 1984 † accepted as Alsacomelita semipalmata G. Karaman, 1984 †
• Abludomelita sexstachya (Gamo, 1977) accepted as Quasimelita sexstachya (Gamo, 1977)
• Abludomelita somovae (Bulyčeva, 1952)
• Abludomelita tuberculata (Nagata, 1965) accepted as Melita tuberculata Nagata, 1965
• Abludomelita unamoena (Hirayama, 1987)
• Abludomelita valida (Shoemaker, 1955) accepted as Melitoides valida (Shoemaker, 1955)
• Abnitocrella eberhardi Karanovic, 2006
• Abnitocrella halsei Karanovic, 2006
• Abnitocrella newmanensis Karanovic, 2006
• Aboilia blessi Becker & Adamczak, 1993 †
• Abormon capillosum Mitra, Pati & Ng, 2021
• Abormon praecalvum Mitra, Pati & Ng, 2021
• Aborolobatea insidiosa Hughes & Lowry, 2009
• Aborolobatea paracheliformis Ledoyer, 1984
• Abortivelum truncatum Berdan & Copeland, 1973 †
• Abrocythereis feishania Hu & Tao, 2008
• Abrocythereis guangdongensis Gou in Gou, Zheng & Huang, 1983 †
• Abrocythereis jyhemouia Hu & Tao, 2008
• Abrocythereis keyi (Kingma, 1948) †
• Abrocythereis punctata (Hu, 1986)
• Abrocythereis ryukyuensis Malz & Tabuki, 1988 †
• Abrocythereis tungyei Hu & Tao, 2008 †
• Abroscelis anchoralis (Chevrolat, 1845)
• Abrotanais geniculum Gellert & Błażewicz, 2018
• Abrote spinimana Philippi, 1857 accepted as Blepharipoda spinosa (H. Milne Edwards & Lucas, 1841)
• Abrsia misophrioides Karanovic, 2008
• Abscondicola humesi Fiers, 1990
• Absonocytheropteron watervalleyense Krutak, 1961 †
• Absonocytheropteron watervalleyensis Krutak, 1961 † accepted as Absonocytheropteron watervalleyense Krutak, 1961 †
• Abyssameira reducta Itô Tat, 1983 accepted as Argestes reductus Itô Tat, 1983
• Abyssaranea rupis Wilson & Hessler, 1974
• Abyssarcturella cidaris Poore & Bardsley, 1992
• Abyssarcturella panope Poore & Bardsley, 1992
• Abyssarcturus averincevi Kussakin & Vasina, 1995
• Abyssianira acutilobi Doti & Roccatagliata, 2006
• Abyssianira argentenensis Menzies, 1962
• Abyssianira bathyalis Just, 1990
• Abyssianira dentifrons Menzies, 1956
• Abyssianira lingula Doti & Roccatagliata, 2006
• Abyssianira tasmaniensis Just, 1990
• Abyssicaprella galatheae McCain, 1966
• Abyssijaera acarina Menzies, 1962 accepted as Katianira acarina (Menzies, 1962)
• Abyssobairdia anisovalva Coles & Whatley, 1989 †
• Abyssobythere guttata Ayress & Whatley, 1989 †
• Abyssobythere inequivalva Ayress, Correge, Passlow & Whatley, 1996
• Abyssocypris (Abyssocypris) tipica Bold, 1974 †
• Abyssocypris (Proabyssocypris) palavensis Pokorny, 1979 † represented as Abyssocypris palavensis Pokorny, 1979 †