1. Species Hydractinia aculeata (Wagner, 1833)
2. Species Hydractinia aggregata Fraser, 1911
3. Species Hydractinia altispina Millard, 1955
4. Species Hydractinia angusta Hartlaub, 1904
5. Species Hydractinia arctica (Jäderholm, 1902)
6. Species Hydractinia arge (Clarke, 1882)
7. Species Hydractinia armata Fraser, 1940
8. Species Hydractinia bayeri Hirohito, 1984
9. Species Hydractinia betkensis (Watson, 1978)
10. Species Hydractinia brachyurae (Hirohito, 1988)
11. Species Hydractinia californica Torrey, 1904
12. Species Hydractinia canalifera Millard, 1957
13. Species Hydractinia carica Bergh, 1887
14. Species Hydractinia carolinae Fraser, 1912
15. Species Hydractinia cryptogonia Hirohito, 1988
16. Species Hydractinia cytaeiformis Vervoort, 2006
17. Species Hydractinia dendritica Hickson & Gravely, 1907
18. Species Hydractinia diogenes Millard, 1959
19. Species Hydractinia disjuncta Fraser, 1938
20. Species Hydractinia echinata (Fleming, 1828)
21. Species Hydractinia epidocleensis Leloup, 1931
22. Species Hydractinia epispongia Fraser, 1938
23. Species Hydractinia galeai Calder & Watling, 2021
24. Species Hydractinia gelinea Watson, 2015
25. Species Hydractinia gorgonoides (Nutting, 1906)
26. Species Hydractinia granulata Hirohito, 1988
27. Species Hydractinia hancocki Fraser, 1938
28. Species Hydractinia ingolfi (Kramp, 1932)
29. Species Hydractinia kaffraria Millard, 1955
30. Species Hydractinia laevispina Fraser, 1922
31. Species Hydractinia longispina Fraser, 1938
32. Species Hydractinia mar (Gasca & Calder, 1993)
33. Species Hydractinia marsupialia Millard, 1975
34. Species Hydractinia michaelseni Broch, 1914
35. Species Hydractinia minoi (Alcock, 1892)
36. Species Hydractinia monocarpa Allman, 1876
37. Species Hydractinia monoon (Hirohito, 1988)
38. Species Hydractinia multispina Fraser, 1938
39. Species Hydractinia multitentaculata (Millard, 1975)
40. Species Hydractinia munita (Calder, 2010)
41. Species Hydractinia nagaoensis Bouillon, Medel & Peña Cantero, 1997
42. Species Hydractinia novaezelandiae Schuchert, 1996
43. Species Hydractinia otagoensis (Schuchert, 1996)
44. Species Hydractinia pacifica Hartlaub, 1905
45. Species Hydractinia parvispina Hartlaub, 1905
46. Species Hydractinia paucispinata Vervoort, 2006
47. Species Hydractinia phialiformis (Antsulevich, 1983)
48. Species Hydractinia piscicola (Komai, 1932)
49. Species Hydractinia polycarpa Fraser, 1938
50. Species Hydractinia polyclina L. Agassiz, 1860
51. Species Hydractinia proboscidea (Hincks, 1868)
52. Species Hydractinia promiscua Galea & Ferry, 2015
53. Species Hydractinia quadrigemina Fraser, 1938
54. Species Hydractinia rugosa Fraser, 1938
55. Species Hydractinia sandrae (Wedler & Larson, 1986)
56. Species Hydractinia sarsii (Steenstrup, 1850)
57. Species Hydractinia spinipapillaris (Hirohito, 1988)
58. Species Hydractinia spiralis Goto, 1910
59. Species Hydractinia symbiolongicarpus Buss & Yund, 1989
60. Species Hydractinia symbiopollicaris Buss & Yund, 1989
61. Species Hydractinia valens Fraser, 1941
62. Species Hydractinia vallini Jäderholm, 1926
63. Species Hydractinia verdi Ritchie, 1907
64. Species Hydractinia yerii (Iwasa, 1934)
65. Subgenus Hydractinia (Euhydractinia) Broch, 1910 accepted as Hydractinia Van Beneden, 1844
66. Subgenus Hydractinia (Stylactis) Allman, 1864 accepted as Stylactis Allman, 1864
    1. Species Hydractinia (Stylactis) ingolfi Kramp, 1932 accepted as Hydractinia ingolfi (Kramp, 1932)
67. Species Hydractinia alderi (Hodge, 1863) accepted as Podocoryna alderi Hodge, 1863 (unaccepted > superseded combination, species inquirenda)
68. Species Hydractinia allmanii Bonnevie, 1898 accepted as Schuchertinia allmanii (Bonnevie, 1898) (basionym)
69. Species Hydractinia americana (Mayer, 1910) accepted as Podocoryna americana (Mayer, 1910) (genus transfer)
70. Species Hydractinia anechinata (Ritchie, 1907) accepted as Podocoryna anechinata Ritchie, 1907
71. Species Hydractinia antonii Miglietta, 2006 accepted as Schuchertinia antonii (Miglietta, 2006) (basionym)
72. Species Hydractinia apicata (Kramp, 1959) accepted as Podocoryna apicata Kramp, 1959
73. Species Hydractinia areolata Alder, 1862 accepted as Podocoryna areolata (Alder, 1862) (genus transfer)
74. Species Hydractinia australis (Schuchert, 1996) accepted as Podocoryna australis Schuchert, 1996
75. Species Hydractinia bella (Hand, 1961) accepted as Podocoryna bella Hand, 1961 (genus transfer)
76. Species Hydractinia borealis (Mayer, 1900) accepted as Podocoryna borealis (Mayer, 1900) (unaccepted > superseded combination, genus transfer)
77. Species Hydractinia borealis (Mereschkowsky, 1878) accepted as Oorhiza borealis Mereschkowsky, 1878
78. Species Hydractinia calcarea Carter, 1877 accepted as Hydrocorella calcarea (Carter, 1977) (genus transfer)
79. Species Hydractinia calderi Bouillon, Medel & Peña Cantero, 1997 accepted as Hydractinia proboscidea (Hincks, 1868) (unaccepted > junior subjective synonym, synonym)
80. Species Hydractinia carcinicola (Hiro, 1939) accepted as Bouillonactinia carcinicola (Hiro, 1939) (genus transfer)
81. Species Hydractinia carnea (M. Sars, 1846) accepted as Podocoryna carnea M. Sars, 1846 (unaccepted > superseded combination)
82. Species Hydractinia clavata Jäderholm, 1905 accepted as Perarella clavata (Jäderholm, 1905) (unaccepted > superseded combination)
83. Species Hydractinia claviformis (Bouillon, 1965) accepted as Hydractinia proboscidea (Hincks, 1868) (unaccepted > junior subjective synonym, synonym)
84. Species Hydractinia conchicola (Yamada, 1947) accepted as Schuchertinia conchicola (Yamada, 1947) (genus transfer)
85. Species Hydractinia constrictura Huang, Xu & Guo, 2015 (unaccepted > unavailable name, electronic publication only, not registered in Zoobank)
86. Species Hydractinia denhami (Thornely, 1904) accepted as Podocoryna denhami Thornely, 1904
87. Species Hydractinia dongshanensis Xu & Huang, 2006 accepted as Podocoryna dongshanensis (Xu & Huang, 2006) (unaccepted > superseded combination)
88. Species Hydractinia dubia (Mayer, 1900) accepted as Podocoryna dubia (Mayer, 1900)
89. Species Hydractinia epiconcha Stechow, 1908 accepted as Schuchertinia epiconcha (Stechow, 1908) (basionym)
90. Species Hydractinia exigua (Haeckel, 1880) accepted as Podocoryna exigua (Haeckel, 1880) (genus transfer)
91. Species Hydractinia fallax Broch, 1914 accepted as Perarella fallax (Broch, 1914) (basionym)
92. Species Hydractinia fucicola (Sars, 1857) accepted as Stylactis fucicola (M. Sars, 1857)
93. Species Hydractinia fuciola (M. Sars, 1857) accepted as Hydractinia fucicola (Sars, 1857) accepted as Stylactis fucicola (M. Sars, 1857) (spelling error)
94. Species Hydractinia grisea Leuckart, 1847 accepted as Hydractinia echinata (Fleming, 1828) (unaccepted > junior subjective synonym)
95. Species Hydractinia guangxiensis Huang, Li & Zhang, 2010 accepted as Podocoryna guangxiensis (Huang, Li & Zhang, 2010) (unaccepted > superseded combination)
96. Species Hydractinia hayamaensis (Hirohito, 1988) accepted as Podocoryna hayamaensis Hirohito, 1988 (basionym)
97. Species Hydractinia hooperii (Sigerfoos, 1899) accepted as Bouillonactinia hooperii (Sigerfoos, 1899) (unaccepted > superseded combination, genus transfer)
98. Species Hydractinia humilis (Hartlaub, 1905) accepted as Podocoryna humilis Hartlaub, 1905 accepted as Podocoryna tenuis (Browne, 1902) (secondary junior homonym of Hydractinia humilis Bonnevie, 1898)
99. Species Hydractinia inabai (Hirohito, 1988) accepted as Bouillonactinia misakiensis (Iwasa, 1934) (unaccepted > junior subjective synonym)
100. Species Hydractinia inermis (Allman, 1872) accepted as Stylactis inermis Allman, 1872 (genus transfer)
101. Species Hydractinia lactea Van Beneden, 1844 accepted as Hydractinia echinata (Fleming, 1828) (unaccepted > junior subjective synonym)
102. Species Hydractinia leizhouensis Huang, Zhang & Yang, 2020 accepted as Podocoryna leizhouensis (Huang, Zhang & Yang, 2020) (unaccepted > superseded combination)
103. Species Hydractinia meteoris (Thiel, 1938) accepted as Paracytaeis meteoris (Thiel, 1938)
104. Species Hydractinia milleri Torrey, 1902 accepted as Schuchertinia milleri (Torrey, 1902) (basionym)
105. Species Hydractinia minima (Trinci, 1903) accepted as Podocorynoides minima (Trinci, 1903)
106. Species Hydractinia minuta Bonnevie, 1898 accepted as Hydractinia carica Bergh, 1887 (unaccepted > junior subjective synonym)
107. Species Hydractinia misakiensis (Iwasa, 1934) accepted as Bouillonactinia misakiensis (Iwasa, 1934) (genus transfer)
108. Species Hydractinia moniliformis Huang, Zhong & Zhang, 2010 accepted as Podocoryna moniliformis (Huang, Zhong & Zhang, 2010) (unaccepted > superseded combination)
109. Species Hydractinia multigranosi (Namikawa, 1991) accepted as Bouillonactinia multigranosi (Namikawa, 1991) (genus transfer)
110. Species Hydractinia nassa (Millard, 1959) accepted as Cytaeis nassa (Millard, 1959) (genus transfer)
111. Species Hydractinia ocellata (Agassiz & Mayer, 1902) accepted as Podocoryna ocellata (Agassiz & Mayer, 1902) (misspelling of genus)
112. Species Hydractinia ornata Bonnevie, 1899 accepted as Hydractinia allmanii Bonnevie, 1898 accepted as Schuchertinia allmanii (Bonnevie, 1898) (synonym)
113. Species Hydractinia phyllosoma Huang & Xu, 2015 (unaccepted > unavailable name, electronic publication only, not registered in Zoobank)
114. Species Hydractinia polytentaculata Xu & Huang, 2006 accepted as Podocoryna polytentaculata (Xu & Huang, 2006) (unaccepted > superseded combination)
115. Species Hydractinia prolifica Fraser, 1948 accepted as Hydractinia rugosa Fraser, 1938 (unaccepted > junior subjective synonym)
116. Species Hydractinia pruvoti Motz-Kossowska, 1905 accepted as Podocoryna pruvoti (Motz-Kossowska, 1905)
117. Species Hydractinia recurvatus Lin, Xu, Huang & Wang, 2010 accepted as Podocoryna recurvata (Lin, Xu, Huang & Wang, 2010) (unaccepted > superseded combination)
118. Species Hydractinia reticulata (Fraser, 1938) accepted as Podocoryna reticulata (Fraser, 1938) (invalid secondary homonym of Hydractina reticulata (Wright, 1861))
119. Species Hydractinia reticulata (Hirohito, 1988) accepted as Schuchertinia reticulata (Hirohito, 1988) (secondary homonym of Hydractina reticulata (Wright, 1861))
120. Species Hydractinia rosea Van Beneden, 1844 accepted as Hydractinia echinata (Fleming, 1828) (unaccepted > junior subjective synonym)
121. Species Hydractinia rubricata Schuchert, 1996 accepted as Clavactinia rubricata (Schuchert, 1996) (basionym)
122. Species Hydractinia sagamiensis (Hirohito, 1988) accepted as Cytaeis sagamiensis (Hirohito, 1988) (genus transfer)
123. Species Hydractinia selena (Mills, 1976) accepted as Hydractinia americana (Mayer, 1910) accepted as Podocoryna americana (Mayer, 1910) (synonym)
124. Species Hydractinia serrata Kramp, 1943 accepted as Clavactinia serrata (Kramp, 1943) (basionym)
125. Species Hydractinia sodalis Stimpson, 1858 accepted as Hydrissa sodalis (Stimpson, 1858) (basionym)
126. Species Hydractinia spiralis Lin, Xu, Huang & Wang, 2010 accepted as Hydractinia taiwanensis Xu, Huang, Lin, Guo & Wang, 2014 accepted as Podocoryna taiwanensis (Xu, Huang, Lin, Guo & Wang, 2014) (invalid junior homonym of Hydractinia spiralis Goto, 1910)
127. Species Hydractinia taiwanensis Xu, Huang, Lin, Guo & Wang, 2014 accepted as Podocoryna taiwanensis (Xu, Huang, Lin, Guo & Wang, 2014) (unaccepted > superseded combination)
128. Species Hydractinia tenuis (Browne, 1902) accepted as Podocoryna tenuis (Browne, 1902) (unaccepted > superseded combination)
129. Species Hydractinia tournieri (Picard & Rahm, 1954) accepted as Cnidostoma fallax Vanhöffen, 1911 (synonym)
130. Species Hydractinia uchidai (Yamada, 1947) accepted as Schuchertinia uchidai (Yamada, 1947) (unaccepted > superseded combination, genus transfer)
131. Species Hydractinia uchidai Nagao, 1961 accepted as Hydractinia nagaoensis Bouillon, Medel & Peña Cantero, 1997
132. Species Hydractinia uniformis Stampar, Tronolone & Morandini, 2006 accepted as Podocoryna uniformis (Stampar, Tronolone & Morandini, 2006) (unaccepted > superseded combination)
133. Species Hydractinia vacuolata Xu & Huang, 2006 accepted as Turritopsis vacuolata (Xu & Huang, 2006) (wrong genus)
134. Species Hydractinia humilis Bonnevie, 1898 (uncertain > taxon inquirendum)
135. Species Hydractinia incerta Van Beneden, 1867 (uncertain > taxon inquirendum)
136. Species Hydractinia reticulata (Wright, 1861) (uncertain > taxon inquirendum)
137. Species Hydractinia siphonis (Stechow, 1921) (uncertain > taxon inquirendum)
138. Species Hydractinia solitaria Van Beneden, 1867 (uncertain > taxon inquirendum)
139. Species Hydractinia tenuissima Van Beneden, 1867 (uncertain > taxon inquirendum)

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