• Hydrosera G.C. Wallich, 1858
• Hydrosera boryana (uncertain > unassessed)
• Hydrosera boryana f. boryana Pantocsek, 1889 (uncertain > unassessed)
• Hydrosera boryana f. hexagona Pantocsek, 1889 (uncertain > unassessed)
• Hydrosera boryana var. hexagona Pantocsek, 1889 (uncertain > unassessed)
• Hydrosera brasiliensis Zimmermann, 1918 (uncertain > unassessed)
• Hydrosera compressa sensu Laporte & Lefebure, 1929 (uncertain > unassessed)
• Hydrosera compressa Wallich, 1858 (uncertain > unassessed)
• Hydrosera javanica (Cleve) (uncertain > unassessed)
• Hydrosera mauritiana Bergon, 1890 (uncertain > unassessed)
• Hydrosera novaecaesarae Boyer, 1895 (uncertain > unassessed)
• Hydrosera petitiana (Leuduger-Fortmorel) F.W. Mills, 1934 accepted as Triceratium petitianum Leuduger-Fortmorel, 1898
• Hydrosera tricornuta Stolterfoth, 1881 (uncertain > unassessed)
• Hydrosera tricoronata Stolterfoth, 1881 (uncertain > unassessed)
• Hydrosera trifoliata (Cleve) De Toni, 1894 accepted as Triceratium trifoliatum Cleve, 1881 †
• Hydrosera trifoliata Cleve, 1881 (uncertain > unassessed)
• Hydrosera triquetra G.C.Wallich
• Hydrosera triquetra var. 4-gona Tempère & Brun, 1889 (uncertain > unassessed)
• Hydrosera triquetra var. hexagona Hustedt, 1937 (uncertain > unassessed)
• Hydrosera triquetra var. tetragona Tempère & Brun in Brun & Tempère, 1889 (uncertain > unassessed)
• Hydrosera triquetra var. triquetra Wallich, 1858 (uncertain > unassessed)
• Hydrosera whampoensis (A.F.Schwarz) Deby, 1891
• Hydrosera whampoensis var. biangulata M. Peragallo, 1897 (uncertain > unassessed)
• Hydrosera whampoensis var. hexagona (Pantocsek) M. Peragallo, 1897 (uncertain > unassessed)
• Hydrosera whampoensis var. mauritania (Bergon) M. Peragallo, 1897 (uncertain > unassessed)
• Hydrosera whampoensis var. tetragona (Tempère & Brun in Brun & Tempère) F.W. Mills, 1934 (uncertain > unassessed)
• Hydrosera whampoensis var. whampoensis (Schwartz) Deby, 1891 accepted as Triceratium whampoense A.F.Schwarz, 1874