Acanthophora J.V.Lamouroux, 1813 (additional source)
Acanthophora dendroides Harvey, 1855 (basis of record)
Acanthophora nayadiformis (Delile) Papenfuss, 1968 (additional source)
Acanthophora spicifera (M.Vahl) Børgesen, 1910 (basis of record)
Acetabularia subg. Acicularia caliculus J.V. Lamouroux, 1824 represented as Acetabularia caliculus J.V.Lamouroux, 1824 (additional source)
Acrochaetium Nägeli, 1858 (additional source)
Acrochaetium candelabrum Børgesen, 1942 (basis of record)
Acrochaetium crassipes (Børgesen) Børgesen, 1915 (additional source)
Acrochaetium klulekaense Stegena (basis of record)
Acrochaetium liagorae Børgesen, 1915 (additional source)
Acrochaetium mauritianum Børgesen, 1942 (basis of record)
Acrochaetium moniliforme (Rosenvinge) Børgesen, 1915 (additional source)
Acrochaetium savianum (Meneghini) Nägeli, 1862 accepted as Colaconema savianum (Meneghini) R.Nielsen, 1994 (additional source)
Acrochaetium secundatum (Lyngbye) Nägeli, 1858 (additional source)
Acrochaetium spongicola Weber Bosse, 1921 (basis of record)
Acrochaetium subseriatum Børgesen, 1932 (additional source)
Acrocystis Zanardini, 1872 (basis of record)
Acrocystis nana Zanardini, 1872 (basis of record)
Acrosorium Zanardini ex Kützing, 1869 (additional source)
Acrosorium acrospermum (J.Agardh) Kylin, 1938 (basis of record)
Acrosorium amphiroae Jaasund, 1976 (basis of record)
Acrosorium deformatum (Suhr) Papenfuss, 1943 (basis of record)
Acrosorium maculatum (Sonder ex Kützing) Papenfuss, 1940 (basis of record)
Acrosorium venulosum (Zanardini) Kylin, 1924 (additional source)
Acrothamnion J.Agardh, 1892 (additional source)
Acrothamnion preissii (Sonder) E.M.Wollaston, 1968 (additional source)
Acrotylus J.Agardh, 1849 (basis of record)
Acrotylus australis J.Agardh, 1849 (basis of record)
Actinotrichia Decaisne, 1842 (basis of record)
Actinotrichia fragilis (Forsskål) Børgesen, 1932 (basis of record)
Aeodes J.Agardh, 1876 (additional source)
Agardhiella F.Schmitz, 1897 (additional source)
Agardhiella subulata (C.Agardh) Kraft & M.J.Wynne, 1979 (additional source)
Aglaothamnion Feldmann-Mazoyer, 1941 (additional source)
Aglaothamnion cordatum (Børgesen) Feldmann-Mazoyer, 1941 (additional source)
Aglaothamnion hookeri (Dillwyn) Maggs & Hommersand, 1993 accepted as Gaillona hookeri (Dillwyn) Athanasiadis, 2016 (additional source)
Aglaothamnion monopodon Børgesen, 1945 (basis of record)
Aglaothamnion sarcodiae Børgesen, 1952 (basis of record)
Aglaothamnion tripinnatum (C.Agardh) Feldmann-Mazoyer, 1941 (additional source)
Ahnfeltiopsis P.C.Silva & DeCew, 1992 (additional source)
Ahnfeltiopsis chnoosporoides (T.Tanaka & P.H.Hô) Masuda, 1993 (basis of record)
Ahnfeltiopsis complicata (Kützing) P.C.Silva & DeCew, 1992 (basis of record)
Ahnfeltiopsis glomerata (J.Agardh) P.C.Silva & DeCew, 1992 (basis of record)
Ahnfeltiopsis polyclada (Kützing) P.C.Silva & DeCew, 1992 (basis of record)
Ahnfeltiopsis vermicularis (C.Agardh) P.C.Silva & DeCew, 1992 (basis of record)
Aiolocolax pulchellus Pocock, 1956 (additional source)
Amansia J.V.Lamouroux, 1809 (basis of record)
Amansia multifida J.V.Lamouroux, 1809 (basis of record)
Amansia rhodantha (Harvey) J.Agardh, 1841 (basis of record)
Amoenothamnion Wollaston, 1968 (basis of record)
Amoenothamnion lycopodioides Stegenga, 1986 (basis of record)
Amphiroa J.V.Lamouroux, 1812 (additional source)
Amphiroa anastomosans Weber-van Bosse, 1904 (basis of record)
Amphiroa anceps (Lamarck) Decaisne, 1842 (basis of record)
Amphiroa angustata (basis of record)
Amphiroa beauvoisii J.V.Lamouroux, 1816 (additional source)
Amphiroa bowerbankii Harvey, 1849 (basis of record)
Amphiroa capensis Areschoug, 1852 (basis of record)
Amphiroa cryptarthrodia Zanardini, 1843 (additional source)
Amphiroa ephedraea (Lamarck) Decaisne, 1842 (basis of record)
Amphiroa foliacea J.V.Lamouroux, 1824 (basis of record)
Amphiroa fragilissima (Linnaeus) J.V.Lamouroux, 1816 (additional source)
Amphiroa gracilis Harvey, 1855 (basis of record)
Amphiroa irregularis Kützing, 1843 (basis of record)
Amphiroa rigida J.V.Lamouroux, 1816 (additional source)
Amphiroa tribulus (J.Ellis & Solander) J.V.Lamouroux, 1816 (basis of record)
Amphiroa ungulata Montagne & Millardet, 1862 (basis of record)
Amphisbetema Weber-van Bosse, 1913 (basis of record)
Amphisbetema indica (J.Agardh) Weber-van Bosse, 1913 (basis of record)
Anadyomene J.V.Lamouroux, 1812 (additional source)
Anadyomene pavonina (J.Agardh) Wille, 1910 (basis of record)
Anadyomene plicata C.Agardh, 1823 (basis of record)
Anadyomene stellata (Wulfen) C.Agardh, 1823 (additional source)
Anadyomene wrightii Harvey ex J.E.Gray, 1866 (basis of record)
Anotrichium Nägeli, 1862 (additional source)
Anotrichium furcellatum (J.Agardh) Baldock, 1976 (additional source)
Anotrichium secundum (Harvey ex J.Agardh) G.Furnari, 1994 (basis of record)
Anotrichium tenue (C.Agardh) Nägeli, 1862 (additional source)
Anthophycus Kützing, 1849 (basis of record)
Anthophycus longifolius (Turner) Kützing, 1849 (basis of record)
Antithamnion Nägeli, 1847 (additional source)
Antithamnion diminuatum Wollaston, 1968 (additional source)
Antithamnion hubbsii E.Y.Dawson, 1962 (basis of record)
Antithamnion pseudoarmatum Stegenga, 1986 (basis of record)
Antithamnion secundum Itono, 1971 (basis of record)
Antithamnion subg. Pteroton adenocladellum R. Norris (basis of record)
Antithamnion subg. Pteroton pinnafolium Wollaston represented as Antithamnion pinnafolium Wollaston, 1968 (basis of record)
Antithamnion subg. Pteroton pterocladellum R. Norris represented as Antithamnion pterocladellum R.E.Norris, 1987 (basis of record)
Aphanothece Nägeli, 1849 (additional source)
Aphanothece castagnei (Kützing) Rabenhorst, 1865 (additional source)
Aphanothece pallida (Kützing) Rabenhorst, 1863 (basis of record)
Aphanothece stagnina (Sprengel) A.Braun, 1863 (additional source)
Apoglossum J.Agardh, 1898 (additional source)
Apoglossum gregarium (E.Y.Dawson) M.J.Wynne, 1985 accepted as Phrix spatulata (E.Y.Dawson) M.J.Wynne, M.Kamiya & J.A.West, 2018 (additional source)
Apoglossum ruscifolium (Turner) J.Agardh, 1898 (additional source)
Apoglossum spathulatum (Sonder) Womersley & Shepley, 1982 (basis of record)
Arthrocardia Decaisne, 1842 (additional source)
Arthrocardia anceps (Yendo) H.W.Johansen, 1984 (basis of record)
Arthrocardia carinata (Kützing) H.W.Johansen, 1984 (basis of record)
Arthrocardia corymbosa (Lamarck) Decaisne, 1842 (basis of record)