• Acetabularia acetabulum (Linnaeus) P.C. Silva, 1952: unknown
• Acetabularia caliculus J.V.Lamouroux, 1824: unknown
• Acetabularia chiavonica Squinabol, 1902 †: unknown
• Acetabularia crenulata J.V. Lamouroux, 1816: unknown
• Acetabularia crenulata J.V.Lamouroux, 1816: unknown
• Acetabularia dentata Solms-Laubach, 1895: unknown
• Acetabularia dentata Solms-Laubach, 1895: unknown
• Acetabularia farlowii Solms-Laubach, 1895: unknown
• Acetabularia farlowii Solms-Laubach, 1895: unknown
• Acetabularia haemmerlingii H.G.Schweiger & Berger, 1975: unknown
• Acetabularia jalakanyakae Sani, Madhu, R.K.Kohli, K.Gupta & Bast, 2021: unknown
• Acetabularia kilneri J.Agardh, 1887: unknown
• Acetabularia major G.Martens, 1866: unknown
• Acetabularia moldavica Barattolo, Ionesi & Ţibuleac, 2019 †: unknown
• Acetabularia peniculus (R.Brown ex Turner) Solms-Laubach, 1895: unknown
• Acetabularia ryukyuensis Okamura & Yamada, 1932: unknown
• Acetabularia schenckii K. Möbius, 1889: unknown
• Acetabularia schenckii Möbius, 1889: unknown
• Acinetospora asiatica Yaegashi, Yamagishi & Kogame, 2015: unknown
• Acinetospora crinita (Carmichael) Sauvageau, 1899: unknown
• Acinetospora filamentosa (Noda) Yaegashi, Uwai & Kogame, 2015: unknown
• Acinetospora nicholsoniae Hollenberg, 1971: unknown
• Acrodiscus vidovichii (Meneghini) Zanardini, 1868: unknown
• Agardhiella coulteri (Harvey) Setchell, 1897: unknown
• Agardhiella floridana (Kylin) P.W.Gabrielsen ex Guimarães & Oliviera, 1996: unknown
• Agardhiella mexicana E.Y.Dawson, 1944: unknown
• Agardhiella ramosissima (Harvey) Kylin, 1932: unknown
• Agardhiella subulata (C.Agardh) Kraft & M.J.Wynne, 1979: unknown
• Alsidium corallinum C.Agardh, 1827: unknown
• Alsidium distichum (Lindenb.) Trevisan: unknown
• Alsidium helminthochorton (Schwendimann) Kützing, 1843: unknown
• Alsidium oliveiranum S.M.Guimarães & M.T.Fujii, 2019: unknown
• Alsidium pacificum E.Y.Dawson, 1959: unknown
• Alsidium pusillum E.Y.Dawson, 1963: unknown
• Alsidium seaforthii (Turner) J.Agardh, 1841: unknown
• Alsidium triquetrum (S.G.Gmelin) Trevisan, 1845: unknown
• Alsidium vagum (Zanardini) Zanardini, 1858: unknown
• Anadyomene cladophoroides (W.J.Gilbert) Guiry & A.R.Sherwood, 2023: unknown
• Anadyomene crispa Chevallier: unknown
• Anadyomene eseptata Gilbert, 1961: unknown
• Anadyomene gigantodictyon M.M.Littler & D.S.Littler, 2012: unknown
• Anadyomene howei D.S.Littler & Littler, 1991: unknown
• Anadyomene lacerata D.S.Littler & Littler, 1991: unknown
• Anadyomene leclancheri Decaisne, 1844: unknown
• Anadyomene lenormandii J.E.Gray: unknown
• Anadyomene linkiana D.S.Littler & M.M.Littler, 1991: unknown
• Anadyomene menziesii (J.E.Gray) J.Agardh, 1887: unknown
• Anadyomene muelleri Sonder: unknown
• Anadyomene pavonina (J.Agardh) Wille, 1910: unknown
• Anadyomene plicata C.Agardh, 1823: unknown
• Anadyomene reticulata Askenasy, 1888: unknown
• Anadyomene rhizoidifera A.B.Joly & Pereira, 1973: unknown
• Anadyomene saldanhae A.B.Joly & E.C.Oliveira, 1969: unknown
• Anadyomene stellata (Wulfen) C.Agardh, 1823: unknown
• Anadyomene wrightii Harvey ex J.E.Gray, 1866: unknown
• Asperococcus bullosus J.V.Lamouroux, 1813: unknown
• Asperococcus cystosirae (Ruprecht) Zanardini: unknown
• Asperococcus ensiformis (Delle Chiaje) M.J.Wynne, 2003: unknown
• Asperococcus fistulosus (Hudson) W.J.Hooker, 1833: unknown
• Asperococcus fragilis (J.Agardh) Zanardini: unknown
• Asperococcus norvegicus Kylin, 1910: unknown
• Asperococcus scaber Kuckuck, 1899: unknown
• Asperococcus tortilis Suhr, 1836: unknown
• Asteromenia anastomosans (Weber-van Bosse) G.W.Saunders, C.E.Lane, C.W.Schneider & Kraft, 2006: unknown
• Asteromenia bermudensis G.W.Saunders, C.E.Lane, C.W.Schneider & Kraft, 2006: unknown
• Asteromenia crenulata G.W.Saunders & Huisman, 2022: unknown
• Asteromenia exanimans G.W.Saunders, C.E.Lane, C.W.Schneider & Kraft, 2006: unknown
• Asteromenia juliannae Huisman & G.W. Saunders, 2022: unknown
• Asteromenia kimberleyensis Huisman & G.W.Saunders, 2018: unknown
• Asteromenia peltata (W.R.Taylor) Huisman & A.J.K.Millar, 1996: unknown
• Asteromenia poeciloderma Huisman & G.W.Saunders, 2018: unknown
• Asteromenia praetermissa G.W.Saunders & Huisman, 2022: unknown
• Asteromenia pseudocoalescens G.W.Saunders, C.E.Lane, C.W.Schneider & Kraft, 2006: unknown
• Avrainvillea amadelpha (Montagne) A.Gepp & E.S.Gepp, 1908: unknown
• Avrainvillea asarifolia Børgesen, 1909: unknown
• Avrainvillea calathina Kraft & Olsen-Stojkovich, 1985: unknown
• Avrainvillea canariensis A.Gepp & E.S.Gepp, 1911: unknown
• Avrainvillea carteri Huisman, 2015: unknown
• Avrainvillea clavatiramea A.Gepp & E.S.Gepp, 1911: unknown
• Avrainvillea corticata Lagourgue & Payri, 2023: unknown
• Avrainvillea cyathiformis D.L.Ballantine & N.E.Aponte, 2003: unknown
• Avrainvillea digitata D.S.Littler & Littler, 1992: unknown
• Avrainvillea elliottii A.Gepp & E.S.Gepp, 1911: unknown
• Avrainvillea erecta (Berkeley) A.Gepp & E.S.Gepp, 1911: unknown
• Avrainvillea fenicalii D.S.Littler, Littler & M.Hay, 1992: unknown
• Avrainvillea fulva (M.Howe) D.S.Littler & Littler, 1992: unknown
• Avrainvillea gardineri A.Gepp & E.S.Gepp, 1908: unknown
• Avrainvillea geppiorum Børgesen, 1913: unknown
• Avrainvillea gracillima Børgesen, 1940: unknown
• Avrainvillea hayi D.S.Littler & Littler, 1992: unknown
• Avrainvillea hollenbergii Trono, 1972: unknown
• Avrainvillea kanakiensis Lagourgue & Payri, 2023: unknown
• Avrainvillea lacerata J.Agardh, 1887: unknown
• Avrainvillea laciniata Lagourgue & Payri, 2023: unknown
• Avrainvillea levis M.Howe, 1905: unknown
• Avrainvillea longicaulis (Kützing) G.Murray & Boodle, 1889: unknown
• Avrainvillea mazei G.Murray & Boodle, 1889: unknown
• Avrainvillea minima Lagourgue, Rousseau & Payri, 2023: unknown
• Avrainvillea mollis Lagourgue & Payri, 2023: unknown
• Avrainvillea montagneana A. & E. S. Gepp: unknown