• Acetabularia acetabulum (Linnaeus) P.C. Silva, 1952: unreported
• Acetabularia caliculus J.V.Lamouroux, 1824: unreported
• Acetabularia chiavonica Squinabol, 1902 †: unreported
• Acetabularia crenulata J.V. Lamouroux, 1816: unreported
• Acetabularia crenulata J.V.Lamouroux, 1816: unreported
• Acetabularia dentata Solms-Laubach, 1895: unreported
• Acetabularia dentata Solms-Laubach, 1895: unreported
• Acetabularia farlowii Solms-Laubach, 1895: unreported
• Acetabularia farlowii Solms-Laubach, 1895: unreported
• Acetabularia haemmerlingii H.G.Schweiger & Berger, 1975: unreported
• Acetabularia jalakanyakae Sani, Madhu, R.K.Kohli, K.Gupta & Bast, 2021: unreported
• Acetabularia kilneri J.Agardh, 1887: unreported
• Acetabularia major G.Martens, 1866: unreported
• Acetabularia moldavica Barattolo, Ionesi & Ţibuleac, 2019 †: unreported
• Acetabularia peniculus (R.Brown ex Turner) Solms-Laubach, 1895: unreported
• Acetabularia ryukyuensis Okamura & Yamada, 1932: unreported
• Acetabularia schenckii K. Möbius, 1889: unreported
• Acetabularia schenckii Möbius, 1889: unreported
• Acrocytis groenlandica Rosenvinge: unreported
• Acrocytis groenlandicus Rosenvinge, 1933: unreported
• Acrospongium ralfsioides Schiffner, 1916: unreported
• Acrothamnion butlerae (Collins) Kylin, 1956: unreported
• Acrothamnion preissii (Sonder) E.M.Wollaston, 1968: unreported
• Aeodes dilatata Yamada: unreported
• Aeodes nitidissima J.Agardh, 1876: unreported
• Agardhiella coulteri (Harvey) Setchell, 1897: unreported
• Agardhiella floridana (Kylin) P.W.Gabrielsen ex Guimarães & Oliviera, 1996: unreported
• Agardhiella mexicana E.Y.Dawson, 1944: unreported
• Agardhiella ramosissima (Harvey) Kylin, 1932: unreported
• Agardhiella subulata (C.Agardh) Kraft & M.J.Wynne, 1979: unreported
• Aiolocolax pulchellus Pocock, 1956: unreported
• Alsidium distichum (Lindenb.) Trevisan: unreported
• Alsidium oliveiranum S.M.Guimarães & M.T.Fujii, 2019: unreported
• Alsidium pacificum E.Y.Dawson, 1959: unreported
• Alsidium pusillum E.Y.Dawson, 1963: unreported
• Alsidium seaforthii (Turner) J.Agardh, 1841: unreported
• Alsidium triquetrum (S.G.Gmelin) Trevisan, 1845: unreported
• Alsidium vagum (Zanardini) Zanardini, 1858: unreported
• Anadyomene cladophoroides (W.J.Gilbert) Guiry & A.R.Sherwood, 2023: unreported
• Anadyomene crispa Chevallier: unreported
• Anadyomene eseptata Gilbert, 1961: unreported
• Anadyomene gigantodictyon M.M.Littler & D.S.Littler, 2012: unreported
• Anadyomene howei D.S.Littler & Littler, 1991: unreported
• Anadyomene lacerata D.S.Littler & Littler, 1991: unreported
• Anadyomene leclancheri Decaisne, 1844: unreported
• Anadyomene lenormandii J.E.Gray: unreported
• Anadyomene linkiana D.S.Littler & M.M.Littler, 1991: unreported
• Anadyomene menziesii (J.E.Gray) J.Agardh, 1887: unreported
• Anadyomene muelleri Sonder: unreported
• Anadyomene pavonina (J.Agardh) Wille, 1910: unreported
• Anadyomene plicata C.Agardh, 1823: unreported
• Anadyomene reticulata Askenasy, 1888: unreported
• Anadyomene rhizoidifera A.B.Joly & Pereira, 1973: unreported
• Anadyomene saldanhae A.B.Joly & E.C.Oliveira, 1969: unreported
• Anadyomene stellata (Wulfen) C.Agardh, 1823: unreported
• Anadyomene wrightii Harvey ex J.E.Gray, 1866: unreported
• Anotrichium anthericephalum (E.Y.Dawson) Baldock, 1976: unreported
• Anotrichium barbatum (C.Agardh) Nägeli, 1862: unreported
• Anotrichium crinitum (Kützing) Baldock, 1976: unreported
• Anotrichium elongatum (Harvey) Baldock, 1976: unreported
• Anotrichium furcellatum (J.Agardh) Baldock, 1976: unreported
• Anotrichium gracile (J.Agardh) Baldock, 1976: unreported
• Anotrichium licmophorum (Harvey) Baldock, 1976: unreported
• Anotrichium multiramosum (Setchell & N.L.Gardner) Baldock, 1976: unreported
• Anotrichium planatum A.J.K.Millar, 1990: unreported
• Anotrichium secundum (Harvey ex J.Agardh) G.Furnari, 1994: unreported
• Anotrichium subtile Baldock, 1976: unreported
• Anotrichium tenue (C.Agardh) Nägeli, 1862: unreported
• Anotrichium towinna Baldock in Womersley, 1998: unreported
• Anotrichium yagii (Okamura) Baldock, 1976: unreported
• Antithamnion adenocladellum R. Norris: unreported
• Antithamnion adenocladellum R.E.Norris, 1987: unreported
• Antithamnion aglandum G.H.Kim & I.K.Lee, 1996: unreported
• Antithamnion amamiense Itono, 1977: unreported
• Antithamnion amphigeneum A.Millar, 1990: unreported
• Antithamnion antillanum Børgesen, 1917: unreported
• Antithamnion armatum (J.Agardh) De Toni, 1903: unreported
• Antithamnion biarmatum Athanasiadis, 1996: unreported
• Antithamnion callocladum Itono, 1971: unreported
• Antithamnion compactum (Grunow) Schiffner, 1944: unreported
• Antithamnion cristatum (Kützing) Schiffner, 1944: unreported
• Antithamnion cruciatum (C.Agardh) Nägeli, 1847: unreported
• Antithamnion decipiens (J.Agardh) Athanasiadis, 1996: unreported
• Antithamnion defectum Kylin, 1925: unreported
• Antithamnion delicatulum (Harvey) De Toni, 1903: unreported
• Antithamnion dendroideum G.M.Smith & Hollenberg, 1943: unreported
• Antithamnion densum (Suhr) M.Howe, 1914: unreported
• Antithamnion diminuatum Wollaston, 1968: unreported
• Antithamnion dispar (J.Agardh) J.Agardh: unreported
• Antithamnion erucacladellum R.E.Norris, 1993: unreported
• Antithamnion gracilentum (Harvey) J.Agardh, 1896: unreported
• Antithamnion hannafordii (Harvey) J.Agardh, 1892: unreported
• Antithamnion hanovioides (Sonder) De Toni, 1903: unreported
• Antithamnion heterocladum Funk, 1955: unreported
• Antithamnion hubbsii E.Y.Dawson, 1962: unreported
• Antithamnion imbricatum (Schousboe ex Suhr) Nägeli: unreported
• Antithamnion kylinii N.L.Gardner, 1927: unreported
• Antithamnion makroklonion Athanasiadis, Garbary & Vandermeulen, 1990: unreported
• Antithamnion nipponicum Yamada & Inagaki, 1935: unreported
• Antithamnion okiense Kajimura, 1987: unreported