1. Species Cystoseira axillaris (Turner) C.Agardh
2. Species Cystoseira cephalornithos (Labill.) C.Agardh
3. Species Cystoseira compressa (Esper) Gerloff & Nizamuddin, 1975
4. Species Cystoseira corniculata (Turner) Zanardini, 1841
5. Species Cystoseira crinita Duby, 1830
6. Species Cystoseira crinitophylla Ercegovic, 1952
7. Species Cystoseira elata Kützing
8. Species Cystoseira filifolia (C.Agardh) C.Agardh
9. Species Cystoseira flaccida Kützing, 1843
10. Species Cystoseira foeniculacea (Linnaeus) Greville, 1830
11. Species Cystoseira humilis Schousboe ex Kützing, 1860
12. Species Cystoseira hypocarpa Kützing, 1854
13. Species Cystoseira masoudii Nizamuddin, 1995
14. Species Cystoseira melanothrix (Kützing) Piccone, 1884
15. Species Cystoseira microcarpa Kützing
16. Species Cystoseira mucronata (Turner) Gaillon
17. Species Cystoseira nigra Bory de Saint-Vincent
18. Species Cystoseira oligacantha (Kützing) Harvey
19. Species Cystoseira oligacantha Kützing
20. Species Cystoseira ornithocephala Sprengel
21. Species Cystoseira paniculata (Turner) C.Agardh
22. Species Cystoseira pelagosae Ercegovic, 1952
23. Species Cystoseira pinnata Kützing
24. Species Cystoseira platyclada Sauvageau, 1912
25. Species Cystoseira platylobium (Mertens) C.Agardh
26. Species Cystoseira pustulata (Ercegovic) Neiva & Serrão, 2022
27. Species Cystoseira pycnoclada Schiffner ex Gerloff & Nizamuddin, 1976
28. Species Cystoseira schiffneri Hamel, 1939
29. Species Cystoseira selaginoides Naccari, 1828
30. Species Cystoseira senegalensis P.J.L.Dangeard, 1938
31. Species Cystoseira sieberi (Bory) Endlicher
32. Species Cystoseira sonderi (Kützing) Piccone, 1886
33. Species Cystoseira spicigera C.Agardh, 1820
34. Species Cystoseira thysigera Postels & Ruprecht, 1840
35. Species Cystoseira tingitana Sauvageau
36. Species Cystoseira tophosa Filarszky
37. Species Cystoseira tuberculata C.Agardh
38. Species Cystoseira wildpretii Nizamuddin, 1995
39. Species Cystoseira abies-marina (S.G.Gmelin) C.Agardh, 1820 accepted as Treptacantha abies-marina (S.G.Gmelin) Kützing, 1843
40. Species Cystoseira abrotanifolia (Linnaeus) C.Agardh, 1820 accepted as Cystoseira foeniculacea (Linnaeus) Greville, 1830 (synonym)
41. Species Cystoseira acanthophora Schiffner, 1926 accepted as Cystoseira schiffneri Hamel, 1939 (synonym)
42. Species Cystoseira acanthophora (J.V.Lamouroux) Chiaje, 1829 accepted as Acanthophora spicifera (M.Vahl) Børgesen, 1910 (synonym)
43. Species Cystoseira adriatica Sauvageau, 1912 accepted as Gongolaria montagnei (J.Agardh) Kuntze, 1891 (unaccepted > junior subjective synonym)
44. Species Cystoseira algeriensis Feldmann, 1945 accepted as Treptacantha algeriensis (Feldmann) Orellana & Sansón, 2019
45. Species Cystoseira amentacea (C.Agardh) Bory de Saint-Vincent, 1832 accepted as Ericaria amentacea (C.Agardh) Molinari & Guiry, 2020 (unaccepted > junior objective synonym)
46. Species Cystoseira articulata J.Agardh, 1848 accepted as Hormophysa cuneiformis (J.F.Gmelin) P.C.Silva, 1987
47. Species Cystoseira aurantia Kützing, 1843 accepted as Cystoseira concatenata f. repens A.D.Zinova & Kalugina accepted as Cystoseira barbata f. aurantia (Kützing) Giaccone, 1985 (synonym)
48. Species Cystoseira baccata (S.G.Gmelin, 1768) P.C.Silva, 1952 accepted as Gongolaria baccata (S.G.Gmelin, 1768) Molinari & Guiry, 2020
49. Species Cystoseira balearica Sauvageau, 1912 accepted as Ericaria brachycarpa (J.Agardh) Molinari & Guiry, 2020 (synonym)
50. Species Cystoseira banksii (Turner) C.Agardh, 1820 accepted as Hormosira banksii (Turner) Decaisne, 1842 (synonym)
51. Species Cystoseira barbata (Stackhouse) C.Agardh, 1820 accepted as Treptacantha barbata (Stackhouse) Orellana & Sansón, 2019
52. Species Cystoseira barbatula Kützing, 1860 accepted as Ericaria barbatula (Kützing) Molinari & Guiry, 2020 (unaccepted > junior objective synonym)
53. Species Cystoseira billardierei (Bory) Endlicher accepted as Hormosira banksii (Turner) Decaisne, 1842
54. Species Cystoseira bosphorica Sauvageau, 1912 accepted as Cystoseira crinita f. bosphorica (Sauvageau) A.D.Zinova & Kalugina, 1974 (synonym)
55. Species Cystoseira brachycarpa J.Agardh, 1896 accepted as Ericaria brachycarpa (J.Agardh) Molinari & Guiry, 2020 (unaccepted > junior objective synonym)
56. Species Cystoseira brownii (Turner) C.Agardh, 1820 accepted as Cystophora brownii (Turner) J.Agardh, 1848
57. Species Cystoseira caespitosa Sauvageau, 1912 accepted as Cystoseira brachycarpa var. balearica (Sauvageau) Giaccone, 1992 accepted as Ericaria brachycarpa (J.Agardh) Molinari & Guiry, 2020 (synonym)
58. Species Cystoseira canariensis Sauvageau, 1912 accepted as Cystoseira humilis Schousboe ex Kützing, 1860
59. Species Cystoseira concatenata (Linnaeus) C.Agardh, 1820 accepted as Cystoseira foeniculacea (Linnaeus) Greville, 1830
60. Species Cystoseira crassipes (Mertens ex Turner) C.Agardh, 1821 accepted as Stephanocystis crassipes (Mertens ex Turner) Draisma, Ballesteros, F.Rousseau & T.Thibaut, 2010 (synonym)
61. Species Cystoseira decipiens (R.Brown ex Turner) C.Agardh, 1821 accepted as Phyllotricha decipiens (R.Brown ex Turner) R.R.M.Dixon & Huisman, 2012 (synonym)
62. Species Cystoseira discors (Linnaeus) C.Agardh, 1828 accepted as Cystoseira foeniculacea (Linnaeus) Greville, 1830 (synonym)
63. Species Cystoseira douglasii Harvey, 1840 accepted as Stephanocystis osmundacea (Turner) Trevisan, 1843 (synonym)
64. Species Cystoseira dubia Valiante, 1883 accepted as Ericaria dubia (Valiante) Neiva & Serrão, 2022
65. Species Cystoseira dumosa Greville ex Sonder, 1846 accepted as Cystophora dumosa (Greville ex Sonder) J.Agardh, 1870 (synonym)
66. Species Cystoseira elegans Sauvageau, 1912 accepted as Treptacantha elegans (Sauvageau) Orellana & Sansón, 2019
67. Species Cystoseira ensifolia C.Agardh, 1824 accepted as Sargassum ensifolium (C.Agardh) J.Agardh, 1873
68. Species Cystoseira epiphytica Schiffner ex Gerloff & Nizamuddin, 1976 accepted as Cystoseira compressa subsp. pustulata (Ercegovic) Verlaque, 2015 (synonym)
69. Species Cystoseira ercegovicii Giaccone, 1973 accepted as Cystoseira foeniculacea (Linnaeus) Greville, 1830 (synonym)
70. Species Cystoseira erica-marina (S.G.Gmelin) Naccari, 1828 accepted as Cystoseira spinosa Sauvageau, 1912 accepted as Gongolaria montagnei (J.Agardh) Kuntze, 1891
71. Species Cystoseira ericoides (Linnaeus) C.Agardh, 1820 accepted as Ericaria selaginoides (Linnaeus) Molinari & Guiry, 2020 (synonym)
72. Species Cystoseira expansa C.Agardh, 1824 accepted as Stephanocystis osmundacea (Turner) Trevisan, 1843 (synonym)
73. Species Cystoseira fibrosa (Hudson) C.Agardh, 1820 accepted as Gongolaria baccata (S.G.Gmelin, 1768) Molinari & Guiry, 2020 (synonym)
74. Species Cystoseira filicina Bory de Saint-Vincent accepted as Cystoseira compressa (Esper) Gerloff & Nizamuddin, 1975
75. Species Cystoseira fimbriata Bory de Saint-Vincent, 1832 accepted as Cystoseira compressa (Esper) Gerloff & Nizamuddin, 1975 (synonym)
76. Species Cystoseira fucoides Ercegovic, 1952 accepted as Cystoseira dubia Valiante, 1883 accepted as Ericaria dubia (Valiante) Neiva & Serrão, 2022
77. Species Cystoseira funkii Schiffner ex Gerloff & Nizamuddin, 1976 accepted as Ericaria funkii (Schiffner ex Gerloff & Nizamuddin) Molinari & Guiry, 2020 (unaccepted > junior objective synonym)
78. Species Cystoseira geminata C.Agardh, 1824 accepted as Stephanocystis geminata (C.Agardh) Draisma, Ballesteros, F.Rousseau & T.Thibaut, 2010 (synonym)
79. Species Cystoseira gerloffi Nizamuddin, 1978 accepted as Cystoseira spinosa var. tenuior (Ercegovic) M.Cormaci, G.Furnari, G.Giaccone, B.Scammacca & D.Serio, 1992 accepted as Cystoseira montagnei var. tenuior (Ercegovic) M.Verlaque, A.Blanfuné, C.F.Boudouresque, T.Thibaut & L.N.Sellam, 2017 (synonym)
80. Species Cystoseira gerloffii Nizamuddin, 1978 accepted as Cystoseira spinosa var. tenuior (Ercegovic) M.Cormaci, G.Furnari, G.Giaccone, B.Scammacca & D.Serio, 1992 accepted as Cystoseira montagnei var. tenuior (Ercegovic) M.Verlaque, A.Blanfuné, C.F.Boudouresque, T.Thibaut & L.N.Sellam, 2017
81. Species Cystoseira gibraltarica (Sauvageau) P.Dangeard, 1949 accepted as Cystoseira mauritanica Sauvageau, 1911 accepted as Treptacantha mauritanica (Sauvageau) Orellana & Sansón, 2019 (synonym)
82. Species Cystoseira graeca Schiffner ex Gerloff & Nizamuddin, 1975 accepted as Cystoseira barbatula Kützing, 1860 accepted as Ericaria barbatula (Kützing) Molinari & Guiry, 2020
83. Species Cystoseira granulata C.Agardh, 1820 accepted as Cystoseira usneoides (Linnaeus) M.Roberts, 1968 accepted as Treptacantha usneoides (Linnaeus) Orellana & Sansón, 2019
84. Species Cystoseira granulata Schousboe, 1892 accepted as Carpodesmia crinita (Bory) Orellana & Sansón, 2019 (synonym)
85. Species Cystoseira grevillei C.Agardh ex Sonder, 1846 accepted as Cystophora grevillei (C.Agardh ex Sonder) J.Agardh, 1848
86. Species Cystoseira hakodatensis (Yendo) Fensholt, 1952 accepted as Stephanocystis hakodatensis (Yendo) Draisma, Ballesteros, F.Rousseau & T.Thibaut, 2010 (synonym)
87. Species Cystoseira hoppii C.Agardh, 1820 accepted as Cystoseira barbata (Stackhouse) C.Agardh, 1820 accepted as Treptacantha barbata (Stackhouse) Orellana & Sansón, 2019
88. Species Cystoseira hyblaea Giaccone, 1985 accepted as Ericaria giacconei D.Serio & G.Furnari, 2021
89. Species Cystoseira indica (Thivy & Doshi) Mairh, 1968 accepted as Polycladia indica (Thivy & Doshi) Draisma, Ballesteros, F.Rousseau & T.Thibaut, 2010 (synonym)
90. Species Cystoseira jabukae Ercegovic, 1952 accepted as Cystoseira spinosa var. tenuior (Ercegovic) M.Cormaci, G.Furnari, G.Giaccone, B.Scammacca & D.Serio, 1992 accepted as Cystoseira montagnei var. tenuior (Ercegovic) M.Verlaque, A.Blanfuné, C.F.Boudouresque, T.Thibaut & L.N.Sellam, 2017 (synonym)
91. Species Cystoseira latifrons (Kützing) De Toni, 1895 accepted as Hormophysa cuneiformis (J.F.Gmelin) P.C.Silva, 1987
92. Species Cystoseira lepidium Ruprecht, 1850 accepted as Stephanocystis geminata (C.Agardh) Draisma, Ballesteros, F.Rousseau & T.Thibaut, 2010
93. Species Cystoseira leptocarpa Kützing accepted as Cystoseira abrotanifolia var. leptocarpa (Kützing) Rodríguez y Femenías
94. Species Cystoseira macrocarpa Kützing, 1854 accepted as Cystoseira foeniculacea (Linnaeus) Greville, 1830
95. Species Cystoseira mauritanica Sauvageau, 1911 accepted as Treptacantha mauritanica (Sauvageau) Orellana & Sansón, 2019
96. Species Cystoseira mediterranea Sauvageau, 1912 accepted as Ericaria mediterranea (Sauvageau) Molinari & Guiry, 2020 (unaccepted > junior objective synonym)
97. Species Cystoseira micheleae Verlaque, Blanfuné, Boudouresque, Thibaut & Sellam, 2017 accepted as Cystoseira foeniculacea (Linnaeus) Greville, 1830
98. Species Cystoseira montagnei J.Agardh, 1842 accepted as Gongolaria montagnei (J.Agardh) Kuntze, 1891 (unaccepted > superseded combination)
99. Species Cystoseira muricata C.Agardh, 1820 accepted as Cystoseira trinodis (Forsskål) C.Agardh, 1820 accepted as Sirophysalis trinodis (Forsskal) Kützing, 1849
100. Species Cystoseira myrica (S.G.Gmelin) C.Agardh, 1820 accepted as Polycladia myrica (S.G.Gmelin) Draima, Ballesteros, F.Rousseau & T.Thibaut, 2010 (synonym)
101. Species Cystoseira myriophylloides Sauvageau, 1912 accepted as Cystoseira humilis var. myriophylloides (Sauvageau) J.H.Price & D.M.John, 1978 (synonym)
102. Species Cystoseira neglecta Setchell & N.L.Gardner, 1917 accepted as Stephanocystis neglecta (Setchell & N.L.Gardner) Draisma, Ballesteros, F.Rousseau & T.Thibaut, 2010 (synonym)
103. Species Cystoseira nodicaulis (Withering) M.Roberts, 1967 accepted as Treptacantha nodicaulis (Withering) Orellana & Sansón, 2019
104. Species Cystoseira nodularia (Mertens) C.Agardh, 1820 accepted as Hormophysa cuneiformis (J.F.Gmelin) P.C.Silva, 1987
105. Species Cystoseira opuntioides Bory de Saint-Vincent ex Montagne, 1846 accepted as Ericaria zosteroides (C.Agardh) Molinari & Guiry, 2020 (synonym)
106. Species Cystoseira osmundacea (Turner) C.Agardh, 1820 accepted as Stephanocystis osmundacea (Turner) Trevisan, 1843 (synonym)
107. Species Cystoseira patentissima Kützing, 1849 accepted as Cystoseira foeniculacea (Linnaeus) Greville, 1830
108. Species Cystoseira pectinata Greville & C.Agardh ex Sonder, 1846 accepted as Cystophora pectinata (Greville & C.Agardh ex Sonder) J.Agardh, 1848
109. Species Cystoseira phyllamphora C.Agardh, 1820 accepted as Coccophora langsdorfii (Turner) Greville, 1830
110. Species Cystoseira planiramea Schiffner ex Gerloff & Nizamuddin, 1975 accepted as Cystoseira compressa subsp. pustulata (Ercegovic) Verlaque, 2015 (synonym)
111. Species Cystoseira platyramosa Ercegovic, 1952 accepted as Cystoseira montagnei var. compressa (Ercegovic) M.Verlaque, A.Blanfuné, C.F.Boudouresque, T.Thibaut & L.N.Sellam, 2017 (synonym)
112. Species Cystoseira prolifera J.Agardh, 1848 accepted as Hormophysa cuneiformis (J.F.Gmelin) P.C.Silva, 1987
113. Species Cystoseira pumila Kützing, 1860 accepted as Cystoseira humilis Schousboe ex Kützing, 1860
114. Species Cystoseira rayssiae E.Ramon, 2000 accepted as Gongolaria rayssiae (Ramon) Molinari & Guiry, 2021 (unaccepted > junior objective synonym)
115. Species Cystoseira rechingeri Schiffner ex Gerloff & Nizamuddin, 1975 accepted as Cystoseira spinosa var. tenuior (Ercegovic) M.Cormaci, G.Furnari, G.Giaccone, B.Scammacca & D.Serio, 1992 accepted as Cystoseira montagnei var. tenuior (Ercegovic) M.Verlaque, A.Blanfuné, C.F.Boudouresque, T.Thibaut & L.N.Sellam, 2017
116. Species Cystoseira rechingerii Schiffner ex Gerloff & Nizamuddin, 1975 accepted as Cystoseira spinosa var. tenuior (Ercegovic) M.Cormaci, G.Furnari, G.Giaccone, B.Scammacca & D.Serio, 1992 accepted as Cystoseira montagnei var. tenuior (Ercegovic) M.Verlaque, A.Blanfuné, C.F.Boudouresque, T.Thibaut & L.N.Sellam, 2017 (synonym)
117. Species Cystoseira retorta (Mertens) C.Agardh, 1820 accepted as Cystophora retorta (Mertens) J.Agardh, 1848 (synonym)
118. Species Cystoseira retroflexa (Labillardière) C.Agardh, 1820 accepted as Cystophora retroflexa (Labillardière) J.Agardh, 1848
119. Species Cystoseira robusta J.Agardh, 1896 accepted as Acrocarpia robusta Womersley, 1964
120. Species Cystoseira sauvageauana Hamel, 1939 accepted as Treptacantha sauvageauana (Hamel) Orellana & Sansón, 2019
121. Species Cystoseira sedoides C.Agardh, 1820 accepted as Ericaria sedoides Neiva & Serrão, 2022
122. Species Cystoseira selaginoides (Linnaeus) Bory de Saint-Vincent, 1832 accepted as Ericaria selaginoides (Linnaeus) Molinari & Guiry, 2020
123. Species Cystoseira setchellii N.L.Gardner, 1913 accepted as Stephanocystis setchellii (N.L.Gardner) Draisma, Ballesteros, F.Rousseau & T.Thibaut, 2010 (synonym)
124. Species Cystoseira sicula Schiffner ex Gerloff & Nizamuddin, 1976 accepted as Cystoseira sauvageauana Hamel, 1939 accepted as Treptacantha sauvageauana (Hamel) Orellana & Sansón, 2019 (synonym)
125. Species Cystoseira siliquastra (Mertens ex Turner) C.Agardh, 1824 accepted as Sargassum siliquastrum (Mertens ex Turner) C.Agardh, 1820
126. Species Cystoseira siliquosa (Linnaeus) C.Agardh, 1820 accepted as Halidrys siliquosa (Linnaeus) Lyngbye, 1819
127. Species Cystoseira sisymbrioides (Turner) Roberts, 1978 accepted as Myagropsis myagroides (Mertens ex Turner) Fensholt, 1955
128. Species Cystoseira spartioides (Turner) C.Agardh accepted as Cystophora moniliformis (Esper) Womersley & Nizamuddin, 1964 (synonym)
129. Species Cystoseira spicata Ercegovic, 1952 accepted as Cystoseira amentacea var. stricta Montagne, 1846 (synonym)
130. Species Cystoseira spinosa Sauvageau, 1912 accepted as Gongolaria montagnei (J.Agardh) Kuntze, 1891 (unaccepted > junior subjective synonym)
131. Species Cystoseira squarrosa De Notaris, 1841 accepted as Treptacantha squarrosa (De Notaris) Orellana & Sansón, 2019
132. Species Cystoseira stricta (Montagne) Sauvageau, 1911 accepted as Cystoseira amentacea var. stricta Montagne, 1846 (synonym)
133. Species Cystoseira subfarcinata (Mertens) C.Agardh, 1824 accepted as Cystophora subfarcinata (Mertens) J.Agardh, 1848
134. Species Cystoseira susanensis Nizamuddin, 1985 accepted as Treptacantha susanensis (Nizamuddin) Orellana & Sansón, 2019
135. Species Cystoseira swartzii (C.Agardh) C.Agardh, 1820 accepted as Sargassum thunbergii (Mertens ex Roth) Kuntze, 1880
136. Species Cystoseira tamariscifolia (Hudson) Papenfuss, 1950 accepted as Ericaria selaginoides (Linnaeus) Molinari & Guiry, 2020 (unaccepted > junior objective synonym)
137. Species Cystoseira thesiophylla Duby, 1830 accepted as Gongolaria baccata (S.G.Gmelin, 1768) Molinari & Guiry, 2020 (synonym)
138. Species Cystoseira thunbergii (Mertens ex Roth) C.Agardh, 1820 (unaccepted)
139. Species Cystoseira tilesii (C.Agardh) C.Agardh, 1823 (unaccepted)
140. Species Cystoseira torulosa (R.Brown ex Turner) C.Agardh, 1820 (unaccepted, synonym)
141. Species Cystoseira trinodis (Forsskål) C.Agardh, 1820 (unaccepted, synonym)
142. Species Cystoseira triquetra C.Agardh, 1820 (unaccepted)
143. Species Cystoseira tristicha Greville & C.Agardh, 1830 (unaccepted)
144. Species Cystoseira turneri (Yendo) M.Roberts, 1978 (unaccepted)
145. Species Cystoseira usneoides (Linnaeus) M.Roberts, 1968 (unaccepted)
146. Species Cystoseira virgata Endlicher & Diesing, 1845 (unaccepted)
147. Species Cystoseira wildprettii Nizamuddin (unaccepted, misspelling)
148. Species Cystoseira zosteroides C.Agardh, 1821 (unaccepted > junior objective synonym)
149. Species Cystoseira australis C.Agardh (uncertain)
150. Species Cystoseira boryana (Kützing) Meneghini (uncertain)
151. Species Cystoseira caudata C.Agardh (uncertain)
152. Species Cystoseira divaricata Kützing (uncertain)
153. Species Cystoseira dorycarpa (Turner) C.Agardh (uncertain)
154. Species Cystoseira flabellata Schousboe (uncertain)
155. Species Cystoseira glomerata Kützing (uncertain)
156. Species Cystoseira gracilis Kützing (uncertain)
157. Species Cystoseira linearifolia Schousboe (uncertain)
158. Species Cystoseira pappafaviana Zanardini (uncertain)
159. Species Cystoseira paradoxa (Turner) C.Agardh (uncertain)
160. Species Cystoseira quercifolia (Turner) C.Agardh (uncertain)
161. Species Cystoseira sauvageauiana Hamel, 1939 (uncertain)
162. Species Cystoseira scoparia J.Agardh (uncertain)
163. Species Cystoseira scoparia Bory ex Lenormand (uncertain)
164. Species Cystoseira scoparia Bory de Saint-Vincent (uncertain)
165. Species Cystoseira selacia Agardh (uncertain)
166. Species Cystoseira siliquastrum (Turner) C.Agardh (uncertain)

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