1. Species Hydrocena canttabrica Prieto, Quinonero-Salgado, Ruiz-Cobo & Alonso, 2022
2. Species Hydrocena cattaroensis (L. Pfeiffer, 1841)
3. Species Hydrocena dubrueiliana (Paladilhe, 1873) †
4. Species Hydrocena gutta Shuttleworth, 1852
5. Species Hydrocena kenyana Connolly, 1929
6. Species Hydrocena moncuccoensis Harzhauser, Neubauer & Esu, 2015 †
7. Species Hydrocena noticola W. H. Benson, 1856
8. Species Hydrocena praecursor T. Yu & Neubauer, 2021 †
9. Species Hydrocena puisseguri Schlickum, 1975 †
10. Species Hydrocena rara (O. Boettger, 1884) †
11. Species Hydrocena reticulata van Benthem Jutting, 1958
12. Species Hydrocena spiralis Wiktor, 1998
13. Species Hydrocena tanzaniensis Verdcourt, 2004
14. Species Hydrocena trolli Schlickum, 1979 †
15. Subgenus Hydrocena (Georissa) W. T. Blanford, 1864 accepted as Georissa W. T. Blanford, 1864
    1. Species Hydrocena (Georissa) blanfordiana (Stoliczka, 1871) accepted as Georissa blanfordiana Stoliczka, 1871 (unaccepted > superseded combination)
    2. Species Hydrocena (Georissa) fraterna (Theobald & Stoliczka, 1872) accepted as Georissa fraterna Theobald & Stoliczka, 1872 (unaccepted combination)
    3. Species Hydrocena (Georissa) frustillum [sic] accepted as Georissa frustrillum (W. H. Benson, 1860) (misspelling)
    4. Species Hydrocena (Georissa) gomantonensis (E. A. Smith, 1893) accepted as Georissa gomantonensis E. A. Smith, 1893 (unaccepted > superseded combination)
    5. Species Hydrocena (Georissa) illex W. H. Benson, 1856 accepted as Georissa illex (W. H. Benson, 1856)
    6. Species Hydrocena (Georissa) liratula (Stoliczka, 1871) accepted as Georissa liratula Stoliczka, 1871 (unaccepted combination )
    7. Species Hydrocena (Georissa) pyxis W. H. Benson, 1856 accepted as Georissa pyxis (W. H. Benson, 1856) (unaccepted combination)
    8. Species Hydrocena (Georissa) rawesiana W. H. Benson, 1860 accepted as Georissa rawesiana (W. H. Benson, 1860) (unaccepted > superseded combination)
    9. Species Hydrocena (Georissa) saritta (W. H. Benson, 1851) accepted as Georissa sarrita (W. H. Benson, 1851) (unaccepted combination and incorrect subsequent spelling)
16. Subgenus Hydrocena (Omphalotropis) L. Pfeiffer, 1851 accepted as Omphalotropis L. Pfeiffer, 1851
    1. Species Hydrocena (Omphalotropis) aurantiaca (Deshayes, 1832) accepted as Omphalotropis aurantiaca (Deshayes, 1832) accepted as Omphalotropis rubens (Quoy & Gaimard, 1832) (unaccepted combination)
    2. Species Hydrocena (Omphalotropis) ceramensis L. Pfeiffer, 1862 accepted as Omphalotropis ceramensis (L. Pfeiffer, 1862) (original combination)
    3. Species Hydrocena (Omphalotropis) dubia (L. Pfeiffer, 1846) accepted as Omphalotropis dubia (L. Pfeiffer, 1846) (unaccepted combination)
    4. Species Hydrocena (Omphalotropis) erosa (Quoy & Gaimard, 1832) accepted as Omphalotropis erosa (Quoy & Gaimard, 1832) (unaccepted combination)
    5. Species Hydrocena (Omphalotropis) expansilabris (L. Pfeiffer, 1854) accepted as Omphalotropis expansilabris (L. Pfeiffer, 1854) (unaccepted combination)
    6. Species Hydrocena (Omphalotropis) exquisita L. Pfeiffer, 1855 accepted as Limborelia exquisita (L. Pfeiffer, 1855) (unaccepted combination)
    7. Species Hydrocena (Omphalotropis) fulvida L. Pfeiffer, 1862 accepted as Cyclotropis carinata (I. Lea, 1856) (a junior synonym)
    8. Species Hydrocena (Omphalotropis) glabrata L. Pfeiffer, 1855 accepted as Omphalotropis glabrata (L. Pfeiffer, 1855) (original combination)
    9. Species Hydrocena (Omphalotropis) globosa (W. H. Benson, 1854) accepted as Omphalotropis globosa (W. H. Benson, 1854) (unaccepted combination)
    10. Species Hydrocena (Omphalotropis) granum L. Pfeiffer, 1855 accepted as Omphalotropis granum (L. Pfeiffer, 1855) (original combination)
    11. Species Hydrocena (Omphalotropis) hieroglyphica (Potiez & Michaud, 1838) accepted as Omphalotropis hieroglyphica (Potiez & Michaud, 1838) (unaccepted combination)
    12. Species Hydrocena (Omphalotropis) huaheinensis L. Pfeiffer, 1855 accepted as Omphalotropis huaheinensis (L. Pfeiffer, 1855) (basionym)
    13. Species Hydrocena (Omphalotropis) malleata L. Pfeiffer, 1855 accepted as Omphalotropis malleata (L. Pfeiffer, 1855) (original combination)
    14. Species Hydrocena (Omphalotropis) maritima Montrouzier, 1863 accepted as Omphalotropis granum (L. Pfeiffer, 1855)
    15. Species Hydrocena (Omphalotropis) multilirata (L. Pfeiffer, 1854) accepted as Omphalotropis multilirata (L. Pfeiffer, 1854) † (unaccepted combination)
    16. Species Hydrocena (Omphalotropis) plicosa (L. Pfeiffer, 1854) accepted as Omphalotropis plicosa (L. Pfeiffer, 1854) (unaccepted combination)
    17. Species Hydrocena (Omphalotropis) pupoides (Anton, 1838) accepted as Omphalotropis pupoides (Anton, 1838) (unaccepted combination)
    18. Species Hydrocena (Omphalotropis) radiata L. Pfeiffer, 1855 accepted as Omphalotropis radiata (L. Pfeiffer, 1855) (original combination)
    19. Species Hydrocena (Omphalotropis) rosea (A. Gould, 1847) accepted as Omphalotropis rosea (A. Gould, 1847) (unaccepted combination)
    20. Species Hydrocena (Omphalotropis) rubens (Quoy & Gaimard, 1832) accepted as Omphalotropis rubens (Quoy & Gaimard, 1832) (unaccepted combination)
    21. Species Hydrocena (Omphalotropis) scitula (A. Gould, 1847) accepted as Omphalotropis scitula (A. Gould, 1847) (unaccepted combination)
    22. Species Hydrocena (Omphalotropis) terebralis (A. Gould, 1847) accepted as Omphalotropis terebralis (A. Gould, 1847) (unaccepted combination)
    23. Species Hydrocena (Omphalotropis) vallata (A. Gould, 1847) accepted as Omphalotropis vallata (A. Gould, 1847) (unaccepted combination)
    24. Species Hydrocena (Omphalotropis) vestita L. Pfeiffer, 1855 accepted as Lyrotropis vestita (L. Pfeiffer, 1855)
17. Species Hydrocena albescens L. Pfeiffer, 1855 accepted as Omphalotropis albescens (L. Pfeiffer, 1855) (unaccepted combination)
18. Species Hydrocena bachmanni Gredler, 1881 accepted as Georissa bachmanni (Gredler, 1881) (original combination)
19. Species Hydrocena belangeri L. Pfeiffer, 1847 accepted as Omphalotropis rubens (Quoy & Gaimard, 1832) (unnecessary nom. nov. pro Cyclostoma aurantiacum, by Pfeiffer treated as a secondary homonym of Annularia aurantiaca Schumacher, 1817)
20. Species Hydrocena brevicula L. Pfeiffer, 1855 accepted as Optediceros breviculum (L. Pfeiffer, 1855) (unaccepted combination)
21. Species Hydrocena brevissima Mousson, 1870 accepted as Georissa brevissima (Mousson, 1870) (original name)
22. Species Hydrocena caledonica Crosse, 1869 accepted as Crossilla caledonica (Crosse, 1869) (original combination)
23. Species Hydrocena cheynei Dohrn & C. Semper, 1862 accepted as Omphalotropis cheynei (Dohrn & C. Semper, 1862) (original combination)
24. Species Hydrocena chinensis L. Pfeiffer, 1857 accepted as Coptocheilus chinensis (L. Pfeiffer, 1857) (original combination)
25. Species Hydrocena clavulus Morelet, 1866 accepted as Omphalotropis clavula (Morelet, 1866) (unaccepted > superseded combination)
26. Species Hydrocena coturnix Crosse, 1867 accepted as Omphalotropis coturnix (Crosse, 1867) (original combination)
27. Species Hydrocena crosseana Gassies, 1869 accepted as Crossilla crosseana (Gassies, 1869) (original combination)
28. Species Hydrocena exquisita L. Pfeiffer, 1855 accepted as Limborelia exquisita (L. Pfeiffer, 1855) (unaccepted combination)
29. Species Hydrocena fasciolata Morelet, 1862 accepted as Cyclotropis carinata (I. Lea, 1856) (unaccepted > junior subjective synonym)
30. Species Hydrocena fischeriana Gassies, 1863 accepted as Omphalotropis fischeriana (Gassies, 1863) (original combination)
31. Species Hydrocena fragilis Pease, 1861 accepted as Omphalotropis fragilis (Pease, 1861) (original combination)
32. Species Hydrocena frustillum [sic] accepted as Georissa frustrillum (W. H. Benson, 1860) (misspelling)
33. Species Hydrocena frustrillum W. H. Benson, 1860 accepted as Georissa frustrillum (W. H. Benson, 1860)
34. Species Hydrocena fulvida L. Pfeiffer, 1862 accepted as Cyclotropis carinata (I. Lea, 1856) (junior synonym)
35. Species Hydrocena granum L. Pfeiffer, 1855 accepted as Omphalotropis granum (L. Pfeiffer, 1855) (unaccepted combination)
36. Species Hydrocena guamensis L. Pfeiffer, 1857 accepted as Omphalotropis guamensis (L. Pfeiffer, 1857) (original combination)
37. Species Hydrocena hidalgoi Gassies, 1869 accepted as Paludinella hidalgoi (Gassies, 1869) (original combination)
38. Species Hydrocena illex W. H. Benson, 1856 accepted as Georissa illex (W. H. Benson, 1856) (original combination)
39. Species Hydrocena insularis Crosse, 1865 accepted as Georissa insularis (Crosse, 1865) (original combination)
40. Species Hydrocena japonica E. von Martens, 1886 accepted as Georissa japonica (E. von Martens, 1886)
41. Species Hydrocena major Morelet, 1866 accepted as Omphalotropis major (Morelet, 1866) (original combination)
42. Species Hydrocena marginata Morelet, 1865 accepted as Optediceros breviculum (L. Pfeiffer, 1855) (unavailable: not Leith, 1853)
43. Species Hydrocena milium (W. H. Benson, 1853) accepted as Angustopila milium (W. H. Benson, 1853) (unaccepted > superseded combination, unaccepted combination)
44. Species Hydrocena monterosatiana (Godwin-Austen & G. Nevill, 1879) accepted as Georissa monterosatiana Godwin-Austen & G. Nevill, 1879 (unaccepted > superseded combination)
45. Species Hydrocena nitida Pease, 1865 accepted as Angustassiminea nitida (Pease, 1865) (original combination)
46. Species Hydrocena oblonga L. Pfeiffer, 1855 accepted as Omphalotropis oblonga (L. Pfeiffer, 1855) (unaccepted combination)
47. Species Hydrocena ovata Pease, 1864 accepted as Assiminea subovata O. Boettger, 1887 (secondary homonym of Assiminea ovata (Krauss, 1848); A. subovata is a replacement name)
48. Species Hydrocena parvula Mousson, 1865 accepted as Assiminea parvula (Mousson, 1865) (original combination)
49. Species Hydrocena purchasi L. Pfeiffer, 1861 accepted as Georissa purchasi (L. Pfeiffer, 1861) (unaccepted > superseded combination)
50. Species Hydrocena pygmaea Gassies, 1867 accepted as Assiminea parvula pygmaea (Gassies, 1867) (basionym)
51. Species Hydrocena pyxis W. H. Benson, 1856 accepted as Georissa pyxis (W. H. Benson, 1856) (original combination)
52. Species Hydrocena radiata L. Pfeiffer, 1855 accepted as Omphalotropis radiata (L. Pfeiffer, 1855) (unaccepted combination)
53. Species Hydrocena raiateensis Mousson, 1869 accepted as Omphalotropis producta (Pease, 1865)
54. Species Hydrocena rawesiana W. H. Benson, 1860 accepted as Georissa rawesiana (W. H. Benson, 1860) (unaccepted > superseded combination)
55. Species Hydrocena rubra Gassies, 1874 accepted as Omphalotropis rubra (Gassies, 1874) (original combination)
56. Species Hydrocena saulae van Benthem Jutting, 1966 accepted as Georissa saulae (van Benthem Jutting, 1966) (original combination)
57. Species Hydrocena scalinella van Benthem Jutting, 1966 accepted as Georissa scalinella (van Benthem Jutting, 1966) (original combination)
58. Species Hydrocena similis Baird, 1873 accepted as Assiminea parvula (Mousson, 1865)
59. Species Hydrocena sirkii L. Pfeiffer, 1847 accepted as Hydrocena cattaroensis (L. Pfeiffer, 1841) (alternate combination)
60. Species Hydrocena turbinata Gassies, 1871 accepted as Crossilla crosseana (Gassies, 1869) (invalid: junior homonym of Hydrocena turbinata Morelet, 1865; H. turrita is a replacement name)
61. Species Hydrocena turrita Gassies, 1880 accepted as Crossilla crosseana (Gassies, 1869)
62. Species Hydrocena variegata Morelet, 1866 accepted as Omphalotropis variegata (Morelet, 1866) (original combination)
63. Species Hydrocena vescoi Dohrn, 1860 accepted as Atropis vescoi (Dohrn, 1860) (original combination)
64. Species Hydrocena vulpina L. Pfeiffer, 1857 accepted as Omphalotropis margarita (L. Pfeiffer, 1851)
65. Subgenus Hydrocena (Hydrocena) Küster, 1844 represented as Hydrocena Küster, 1844
    1. Species Hydrocena (Hydrocena) dubrueilliana [sic] † accepted as Hydrocena dubrueiliana (Paladilhe, 1873) † (unaccepted > misspelling - incorrect subsequent spelling)
    2. Species Hydrocena (Hydrocena) minutissima (G. B. Sowerby I, 1832) accepted as Georissa minutissima (G. B. Sowerby I, 1832) (unaccepted combination)
    3. Species Hydrocena (Hydrocena) albescens L. Pfeiffer, 1855 represented as Hydrocena albescens L. Pfeiffer, 1855 accepted as Omphalotropis albescens (L. Pfeiffer, 1855)
    4. Species Hydrocena (Hydrocena) brevicula L. Pfeiffer, 1855 represented as Hydrocena brevicula L. Pfeiffer, 1855 accepted as Optediceros breviculum (L. Pfeiffer, 1855)
    5. Species Hydrocena (Hydrocena) bridgesi L. Pfeiffer, 1855 represented as Hydrocena bridgesi L. Pfeiffer, 1855
    6. Species Hydrocena (Hydrocena) cattaroensis (L. Pfeiffer, 1841) represented as Hydrocena cattaroensis (L. Pfeiffer, 1841)
    7. Species Hydrocena (Hydrocena) cornea L. Pfeiffer, 1855 represented as Hydrocena cornea L. Pfeiffer, 1855
    8. Species Hydrocena (Hydrocena) exserta L. Pfeiffer, 1855 represented as Hydrocena exserta L. Pfeiffer, 1855
    9. Species Hydrocena (Hydrocena) gutta Shuttleworth, 1852 represented as Hydrocena gutta Shuttleworth, 1852
    10. Species Hydrocena (Hydrocena) oblonga L. Pfeiffer, 1855 represented as Hydrocena oblonga L. Pfeiffer, 1855 accepted as Omphalotropis oblonga (L. Pfeiffer, 1855)
    11. Species Hydrocena (Hydrocena) obtusa L. Pfeiffer, 1855 represented as Hydrocena obtusa L. Pfeiffer, 1855
    12. Species Hydrocena (Hydrocena) puisseguri Schlickum, 1975 † represented as Hydrocena puisseguri Schlickum, 1975 †
    13. Species Hydrocena (Hydrocena) pyramis L. Pfeiffer, 1855 represented as Hydrocena pyramis L. Pfeiffer, 1855
    14. Species Hydrocena (Hydrocena) solidula L. Pfeiffer, 1855 represented as Hydrocena solidula L. Pfeiffer, 1855
    15. Species Hydrocena (Hydrocena) trolli Schlickum, 1979 † represented as Hydrocena trolli Schlickum, 1979 †
66. Species Hydrocena atavina Stache, 1889 † (uncertain > taxon inquirendum)
67. Species Hydrocena bridgesi L. Pfeiffer, 1855 (uncertain > taxon inquirendum)
68. Species Hydrocena cerea L. Pfeiffer, 1857 (uncertain > taxon inquirendum)
69. Species Hydrocena cornea L. Pfeiffer, 1855 (uncertain > taxon inquirendum)
70. Species Hydrocena diaphana Gassies, 1863 (uncertain > nomen dubium)
71. Species Hydrocena exserta L. Pfeiffer, 1855 (uncertain > taxon inquirendum)
72. Species Hydrocena lirata Morelet, 1862 (uncertain > taxon inquirendum)
73. Species Hydrocena navigatorum L. Pfeiffer, 1857 (uncertain > taxon inquirendum)
74. Species Hydrocena obtusa L. Pfeiffer, 1855 (uncertain > taxon inquirendum)
75. Species Hydrocena pyramis L. Pfeiffer, 1855 (uncertain > taxon inquirendum)
76. Species Hydrocena scherzeri Zelebor, 1867 (uncertain > taxon inquirendum)
77. Species Hydrocena solidula L. Pfeiffer, 1855 (uncertain > taxon inquirendum)
78. Species Hydrocena turbinata Morelet, 1865 (uncertain > taxon inquirendum)

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