• Abacella cornuta Shuysky, 1973 †
• Abacella delicatula J.H.Johnson, 1964 †
• Abacella dentata Shuysky, 1973 †
• Abacella pertusa Maslov, 1956 †
• Abacella pustulata Shuysky, 1973 †
• Abacella stellata Shuysky, 1991 †
• Acanthochonia barrandei Hinde, 1884 † accepted as Ischadites barrandei (Hinde) S.J.Gould & M.J.Katz, 1975 †
• Acanthochonia devonica Schlüter, 1887 † accepted as Ischadites devonicus (Schlüter) Rauff, 1893 †
• Acanthococcus anglicus A.W.Bennett, 1888 accepted as Glochiococcus anglicus (A.W.Bennett) De Toni, 1888
• Acanthococcus minor Hansgirg, 1885 accepted as Glochiococcus minor (Hansgirg) De Toni & Levi
• Acanthococcus palustris Hansgirg A., 1888 accepted as Trochiscia stagnalis Hansgirg, 1889
• Acanthocodium fragile Suringar, 1867 accepted as Codium fragile (Suringar) Hariot, 1889
• Acanthosphaera tenuispina Korshikov, 1953 accepted as Acanthosphaera zachariasii Lemmermann, 1899
• Acanthosphaera zachariasii Lemmermann, 1899
• Acetabularia acetabulum (Linnaeus) P.C. Silva, 1952
• Acetabularia antillana (Solms-Laubach) Egerod, 1952 accepted as Chalmasia antillana Solms-Laubach, 1895
• Acetabularia caliculus J.V.Lamouroux, 1824
• Acetabularia caraibica Kützing, 1856 accepted as Acetabularia crenulata J.V.Lamouroux, 1816
• Acetabularia caribaeum Lamarck, 1816 accepted as Acetabularia crenulata J.V.Lamouroux, 1816
• Acetabularia chiavonica Squinabol, 1902 †
• Acetabularia clavata Yamada, 1934 accepted as Parvocaulis clavatus (Yamada) S.Berger, U.Fettweiss, S.Gleissberg, L.B.Liddle, U.Richter, H.Sawitzky & G.C.Zuccarello, 2003
• Acetabularia crenulata J.V. Lamouroux, 1816
• Acetabularia crenulata J.V.Lamouroux, 1816
• Acetabularia crenulata var. major Sonder, 1871 accepted as Acetabularia major G.Martens, 1866
• Acetabularia crenulata var. monodisca Børgesen, 1936
• Acetabularia dentata Solms-Laubach, 1895
• Acetabularia dentata Solms-Laubach, 1895
• Acetabularia denudata Zanardini, 1878 accepted as Acetabularia major G.Martens, 1866
• Acetabularia exigua Solms-Laubach, 1895 accepted as Parvocaulis polyphysoides (P.Crouan & H.Crouan) S.Berger & al. ex J.N.Norris & D.L.Ballantine, 2023
• Acetabularia farlowii Solms-Laubach, 1895
• Acetabularia farlowii Solms-Laubach, 1895
• Acetabularia gigas Solms-Laubach, 1895 accepted as Acetabularia major G.Martens, 1866
• Acetabularia haemmerlingii H.G.Schweiger & Berger, 1975
• Acetabularia integra J.V.Lamouroux accepted as Acetabularia acetabulum (Linnaeus) P.C. Silva, 1952
• Acetabularia jalakanyakae Sani, Madhu, R.K.Kohli, K.Gupta & Bast, 2021
• Acetabularia kilneri J. Agardh represented as Acetabularia kilneri J.Agardh, 1887
• Acetabularia kilneri J.Agardh, 1887
• Acetabularia major G. Martens represented as Acetabularia major G.Martens, 1866
• Acetabularia major G.Martens, 1866
• Acetabularia major var. gigas (Solms-Laubach) Valet, 1969 accepted as Acetabularia major G.Martens, 1866
• Acetabularia mediterranea J.V.Lamouroux, 1816 accepted as Acetabularia acetabulum (Linnaeus) P.C. Silva, 1952
• Acetabularia minutissima Okamura, 1912 accepted as Parvocaulis parvulus (Solms-Laubach) S.Berger, Fettweiss, Gleissberg, Liddle, U.Richter, Sawitzky & Zuccarello, 2003
• Acetabularia miocenica Andrussow, 1887 † accepted as Acicularia andrussowii Solms-Laubach, 1895 †
• Acetabularia moebii Solms-Laubach, 1895 accepted as Parvocaulis parvulus (Solms-Laubach) S.Berger, Fettweiss, Gleissberg, Liddle, U.Richter, Sawitzky & Zuccarello, 2003
• Acetabularia moldavica Barattolo, Ionesi & Ţibuleac, 2019 †
• Acetabularia myriospora A.B.Joly & Cordeiro-Marino, 1965 accepted as Parvocaulis myriosporus (A.B.Joly & Cordeiro-Marina) C.W.Nascimento Moura & J.C.DeAndrade, 2014
• Acetabularia parvula Solms-Laubach, 1895 accepted as Parvocaulis parvulus (Solms-Laubach) S.Berger, Fettweiss, Gleissberg, Liddle, U.Richter, Sawitzky & Zuccarello, 2003
• Acetabularia parvula var. americana W.R.Taylor, 1945 accepted as Parvocaulis parvulus (Solms-Laubach) S.Berger, Fettweiss, Gleissberg, Liddle, U.Richter, Sawitzky & Zuccarello, 2003
• Acetabularia peniculus (R.Brown ex Turner) Solms-Laubach, 1895
• Acetabularia peniculus var. cliftonii (Harvey) Solms-Laubach, 1895 accepted as Acetabularia peniculus (R.Brown ex Turner) Solms-Laubach, 1895
• Acetabularia philippinensis Gilbert, 1943 accepted as Acetabularia ryukyuensis Okamura & Yamada, 1932
• Acetabularia polyphysoides P.Crouan & H.Crouan, 1865 accepted as Parvocaulis polyphysoides (P.Crouan & H.Crouan) S.Berger & al. ex J.N.Norris & D.L.Ballantine, 2023
• Acetabularia polyphysoides f. deltoidea (M.Howe) Collins, 1909 accepted as Polyphysa myriospora (A.B.Joly & Cordiero-Marinha) S.Berger & M.J.Kaever, 1992 accepted as Acetabularia myriospora A.B.Joly & Cordeiro-Marino, 1965 accepted as Parvocaulis myriosporus (A.B.Joly & Cordeiro-Marina) C.W.Nascimento Moura & J.C.DeAndrade, 2014
• Acetabularia pusilla (M.Howe) Collins, 1909 accepted as Parvocaulis pusillus (M.Howe) S.Berger, U.Fettweiss, S.Gleissberg, L.B.Liddle, U.Richter, H.Sawitzky & G.C.Zuccarello, 2003
• Acetabularia roxasii Trono, A.E.Santiago & Ganzon-Fortes, 1978 accepted as Acetabularia ryukyuensis Okamura & Yamada, 1932
• Acetabularia ryukyuensis Okamura & Yamada, 1932
• Acetabularia ryukyuensis Okamura & Yamada, 1932 represented as Acetabularia ryukyuensis Okamura & Yamada, 1932
• Acetabularia ryukyuensis var. philippinensis (Gilbert) Valet, 1943 accepted as Acetabularia ryukyuensis Okamura & Yamada, 1932
• Acetabularia ryukyuensis var. philippinensis (Gilbert) Valet, 1943 represented as Acetabularia ryukyuensis var. philippinensis (Gilbert) Valet, 1943 accepted as Acetabularia ryukyuensis Okamura & Yamada, 1932
• Acetabularia schenckii K. Möbius, 1889
• Acetabularia schenckii Möbius, 1889
• Acetabularia suhrii Solms-Laubach, 1895 accepted as Acetabularia caliculus J.V.Lamouroux, 1824
• Acetabularia tsengiana Egerod, 1952 accepted as Parvocaulis exiguus (Solms-Laubach) S.Berger, U.Fettweiss, S.Gleissberg, L.B.Liddle, U.Richter, H.Sawitzky & G.C.Zuccarello, 2003
• Acetabularia velasquezii Trono, A.B.Santiago & Ganzon-Fortes, 1978 accepted as Parvocaulis parvulus (Solms-Laubach) S.Berger, Fettweiss, Gleissberg, Liddle, U.Richter, Sawitzky & Zuccarello, 2003
• Acetabularia wettsteinii Schussnig, 1930 accepted as Parvocaulis parvulus (Solms-Laubach) S.Berger, Fettweiss, Gleissberg, Liddle, U.Richter, Sawitzky & Zuccarello, 2003
• Acetabulum caraibicum (Kützing) M.A.Howe, 1901 accepted as Acetabularia crenulata J.V.Lamouroux, 1816
• Acetabulum crenulatum (J.V.Lamouroux) Kuntze, 1891 accepted as Acetabularia crenulata J.V.Lamouroux, 1816
• Acetabulum marinum Tournefort, 1760 accepted as Acetabularia acetabulum (Linnaeus) P.C. Silva, 1952
• Acetabulum mediterraneum Lamarck, 1816 accepted as Acetabularia acetabulum (Linnaeus) P.C. Silva, 1952
• Acetabulum miocenicum (Andrussow) Kuntze, 1891 † (uncertain)
• Acetabulum polyphysoides
• Acetabulum polyphysoides f. deltoideum M.Howe, 1909 accepted as Polyphysa myriospora (A.B.Joly & Cordiero-Marinha) S.Berger & M.J.Kaever, 1992 accepted as Acetabularia myriospora A.B.Joly & Cordeiro-Marino, 1965 accepted as Parvocaulis myriosporus (A.B.Joly & Cordeiro-Marina) C.W.Nascimento Moura & J.C.DeAndrade, 2014
• Acetabulum pusilla M.Howe (uncertain)
• Acetabulum pusillum M.Howe, 1909 accepted as Parvocaulis pusillus (M.Howe) S.Berger, U.Fettweiss, S.Gleissberg, L.B.Liddle, U.Richter, H.Sawitzky & G.C.Zuccarello, 2003
• Achoma brachiatum Novis & Visnovsky, 2012
• Acicularia alaica Maslov, 1956 †
• Acicularia albrightii Johnson & Kaska
• Acicularia americana Konishi & Epis
• Acicularia andrusovii Livental, 1946 †
• Acicularia andrussowii Solms-Laubach, 1895 † (uncertain)
• Acicularia antiqua Pia, 1936 †
• Acicularia archiacii L.Morellet & J.Morellet, 1922 †
• Acicularia azerbaidganica Livental, 1946 †
• Acicularia clapei Jaffrezo
• Acicularia clavata L.Morellet & J.Morellet, 1922 †
• Acicularia comanchensis Johnson (uncertain)
• Acicularia cornigera L.Morellet & J.Morellet, 1922 †
• Acicularia dubossariensis Maslov, 1961 †
• Acicularia dubossariensis var. minima Maslov, 1961 †
• Acicularia dyumatsenae Pia
• Acicularia endoi Praturlon, 1964 †
• Acicularia eocaenica Munier-Chalmas ex L.Morellet & J.Morellet, 1922 †
• Acicularia ferganensis Maslov, 1956 †
• Acicularia ferganensis var. turquestanica Maslov, 1956 †
• Acicularia gracilis L.Morellet & J.Morellet (uncertain)
• Acicularia guatemalaica Johnson & Kaska (uncertain)
• Acicularia hebertii L.Morellet & J.Morellet, 1922 †
• Acicularia indica Varma
• Acicularia intermedia Dragastan, 1967 †
• Acicularia jurassica J.H.Johnson