• Cysta Cleve, 1900 accepted as Pterosperma Pouchet, 1893
• Cystacanthus T. Anderson, 1867
• Cystactinia Brooks, 1964 † (uncertain > nomen dubium)
• Cystactinia ocalana Brooks, 1964 †
• Cystactis Vosmaer, 1885 (unaccepted)
• Cystacythereis accepted as Cistacythereis Uliczny, 1969 †
• Cystagora Stafford, 1905 (uncertain)
• Cystalia Haeckel, 1888 (uncertain)
• Cystammina Neumayr, 1889
• Cystammina aguayoi Bermudez & Acosta, 1940
• Cystammina galeata (Brady, 1881)
• Cystammina pauciloculata (Brady, 1879)
• Cystammina spiculifera Zheng, 1988
• Cystamminella Lukina, 1980 † accepted as Buzasina Loeblich & Tappan, 1985 † [Family: Haplophragmoididae]
• Cystamminella Myatlyuk, 1966 † (uncertain) [Family: Sarcomastigota (awaiting allocation)]
• Cystamminella galeata (Brady, 1881) † accepted as Buzasina galeata (Brady, 1881) †
• Cystamminoides Zheng in Zheng & Fu, 2001
• Cystamminoides quadriloculus Zheng & Fu, 2001
• Cystamminoides triloculus Zheng & Fu, 2001
• Cystangium R. Singer & A.H. Smith, 1960 accepted as Russula Persoon, 1796
• Cystangium balpineum Grgur., 1997
• Cystangium crichtonii G.W. Beaton, Pegler & T.W.K. Young, 1986
• Cystangium depauperatum Singer & A.H. Sm., 1960
• Cystangium phymatodisporum G.W. Beaton, Pegler & T.W.K. Young, 1984
• Cystangium pineti Singer, 1985
• Cystangium rodwayi (Massee) A.H. Sm., 1963
• Cystangium sessile (Massee & Rodway ex Rodway) Singer & A.H. Sm., 1960
• Cystanthe R. Brown, 1810 accepted as Richea R. Brown, 1810
• Cystaster Hall, 1871 †
• Cystauletes King, 1943 †
• Cyste Dulac, 1867 accepted as Cystopteris Bernhardi, 1805
• Cystea J.E. Smith, 1828 accepted as Cystopteris Bernhardi, 1805
• Cystechinus A. Agassiz, 1879
• Cystechinus clypeatus A. Agassiz, 1879 accepted as Urechinus clypeatus (A. Agassiz, 1879)
• Cystechinus fragilis Koehler, 1908 accepted as Urechinus wyvilli (A. Agassiz, 1879) accepted as Cystechinus wyvillii A. Agassiz, 1879
• Cystechinus giganteus (A. Agassiz, 1898)
• Cystechinus loveni A. Agassiz, 1898 accepted as Urechinus loveni (A. Agassiz, 1898)
• Cystechinus purpureus A. Agassiz & H.L. Clark, 1907 accepted as Urechinus loveni (A. Agassiz, 1898)
• Cystechinus rathbuni A. Agassiz, 1898 accepted as Pilematechinus rathbuni (A. Agassiz, 1898)
• Cystechinus reticulatus (H.L. Clark, 1924) accepted as Urechinus reticulatus H.L. Clark, 1913
• Cystechinus vesica A. Agassiz, 1879 accepted as Pilematechinus vesica (A. Agassiz, 1879)
• Cystechinus wyvilli A. Agassiz, 1879 accepted as Cystechinus wyvillii A. Agassiz, 1879
• Cystechinus wyvillii A. Agassiz, 1879
• Cysteiniphilum Liu et al., 2017
• Cystelasma Miller, 1892 †
• Cystenides McIntosh, 1876 accepted as Cistenides Malmgren, 1866
• Cysteocercus Agassiz, 1846 accepted as Taenia Linnaeus, 1758
• Cysteocheila (uncertain)
• Cysteocheila cracens Drake & Ruhoff, 1965 accepted as Cysteochila cracentis Drake, 1954
• Cysteochila Stål, 1873
• Cysteochila brunnea Hacker, 1928
• Cysteochila camelinus Hacker, 1927 accepted as Bunotingis camelina (Hacker, 1927)
• Cysteochila cracentis Drake, 1954
• Cysteochila franzeni Drake, 1942 accepted as Cysteochila tricolor (Hacker, 1929)
• Cysteochila hackeri Drake, 1939
• Cysteochila taeniophora Horváth, 1925 accepted as Parada taeniophora (Horváth, 1925)
• Cysteochila tricolor (Hacker, 1929)
• Cysteodemus Leconte, 1851
• Cysteodemus armatus Leconte
• Cysteodemus vittatus LeConte, 1853 accepted as Megetra vittatus (LeConte, 1853)
• Cysteodemus wislizeni LeConte, 1851
• Cysteodictyina Carter, 1880 (uncertain)
• Cysteognathus Agassiz, 1846 (unaccepted)
• Cysteonevra Agassiz, 1846 accepted as Cystineura Boisduval, 1836
• Cysteophora Hulst, 1900 (uncertain)
• Cysteophyllum Agassiz, 1846 † (unaccepted)
• Cysteopteryx Hulst, 1896 (uncertain)
• Cysteorracha Kirkaldy, 1908
• Cysteorracha cactifera Kirkaldy, 1908
• Cysteorrhacha Kirkaldy, 1908 (uncertain)
• Cysteosaurus Agassiz, 1846 † (unaccepted)
• Cysteosoma Agassiz, 1846 accepted as Cystisoma Guérin-Méneville, 1842
• Cysteosoma Bovallius, 1886 accepted as Cystisoma Guérin-Méneville, 1842
• Cystercus Dun, 1854 accepted as Taenia Linnaeus, 1758
• Cystericus Lee, 1840 accepted as Taenia Linnaeus, 1758
• Cystia Deshayes, 1844 (uncertain)
• Cystia Renier, 1804 (unaccepted)
• Cystiactis Milne-Edwards, 1857
• Cystiactis antarctica Clubb, 1908 accepted as Dactylanthus antarcticus (Clubb, 1908)
• Cystiactis eugenia Duchassaing & Michelotti, 1864
• Cystiactis eydouxii Milne Edwards, 1857
• Cystiactis gaudichaudi Milne Edwards, 1857
• Cystiactis koellikeri Pax, 1910
• Cystiactis retifera Stuckey accepted as Phlyctenactis tuberculosa (Quoy & Gaimard, 1833)
• Cystiactis tuberculosa (Quoy & Gaimard, 1833) Haddon, 1896 accepted as Phlyctenactis tuberculosa (Quoy & Gaimard, 1833)
• Cysticaercus Slawikowski, 1819 accepted as Cysticercus Rudolphi, 1801 accepted as Taenia Linnaeus, 1758
• Cysticamara Kozlowski, 1938 † (unaccepted > nomen nudum) [Family: Cnidaria (awaiting allocation)]
• Cysticamara Kozlowski, 1948 † [Family: Camaroidea (awaiting allocation)]
• Cysticamaridae †
• Cysticapnos P. Miller, 1754
• Cysticercoideum Parona, 1901 (unaccepted)
• Cysticercus Goldberg, 1855 accepted as Taenia Linnaeus, 1758
• Cysticercus Rudolphi, 1801 accepted as Taenia Linnaeus, 1758
• Cysticercus Zeder in Goeze, 1800 accepted as Taenia Linnaeus, 1758
• Cysticercus ovis Cobbold, 1869 accepted as Taenia ovis (Cobbold, 1869)
• Cysticerkus Schneidemühl, 1896 accepted as Cysticercus Rudolphi, 1801 accepted as Taenia Linnaeus, 1758
• Cysticerrus Braun, 1883 accepted as Cysticercus Rudolphi, 1801 accepted as Taenia Linnaeus, 1758
• Cysticerus Bischoff, 1840 accepted as Cysticercus Rudolphi, 1801 accepted as Taenia Linnaeus, 1758
• Cystichnium Hu & Wu, 1993 † (uncertain)
• Cysticola Lesson, 1831 accepted as Cisticola Kaup, 1829