Species (15.149)
- Ophryocerca ovum Ehrenberg 1831
- Ophryoglena citrea Ehrenberg 1831
- Ophryodendron abietinum Claparède & Lachmann 1859
- Ophryoglena bacterocaryon Roque et al./Savoie? 1965
- Ophryodendron procellanum Kent 1882
- Ophryoglena citreum Ehrenberg 1831
- Ophryoglena collini Lichtenstein 1921
- Ophryoglena faurei Savoie 1962
- Ophryoglena flava Ehrenberg 1833
- Ophryoglena vorax Smith 1897
- Ophryoglena viridis Penard 1922
- Ophryoscolex bicoronatus -> LB0002: 76
- Opisthonecta bivacuolata Foissner 1978
- Opisthonecta minima Foissner 1975
- Opisthostomatella bengalense Ghosh 1928
- Opisthotricha muscorum Kahl 1932
- Opisthotricha ovata Kahl 1932
- Opisthotricha euglenivora Kahl 1932
- Opisthotricha parallella Engelmann 1862
- Opisthotricha procera Kahl 1932
- Opisthotricha parallela Engelmann 1862
- Opisthotricha similis Engelmann 1862
- Opisthotricha sphagni Kahl 1932
- Opisthotricha terrestris Horváth 1956
- Opisthotricha terricola Gellert 1957
- Orbopercularia berberina Lust 1950
- Orbopercularia nodosa Foissner 1979
- Orbopyxidiella stammeri Lust 1950
- Orchitophrya stellarum Cépède 1907
- Oncosonderia tubigula Kahl 1930
- Onychaspis polystyla Stein 1859
- Onychodromus grandis Stein 1859
- Onychodromopsis flexilis Stokes 1887
- Opalina cordiformis Perty 1852
- Onychodromus quadricornutus Foissner, Schlegel & Prescott 1987
- Opalina tritonis Perty 1852
- Opalinopsis sepiolae Foettinger 1881
- Opercularia coarctata Claparède & Lachmann 1858
- Opercularia confervarum Faure-Fremiet 1905
- Opercularia confusa Stiller 1940
- Opercularia constricta Kellicott 1885
- Opercularia corethrae Keiser 1921
- Opercularia cylindrata Wrzesniowski 1870
- Opercularia curvicaulis Penard 1922
- Opercularia dytiscidarum Faure-Fremiet 1905
- Opercularia fabrei Faure-Fremiet 1905
- Opercularia elongata Kellicott 1884
- Opercularia gammari Faure-Fremiet 1905
- Opercularia faurei Collin 1909
- Opercularia glomerata Roux 1901
- Opercularia gracilis Faure-Fremiet 1904
- Opercularia henneguyi Faure-Fremiet 1905
- Opercularia humilis Kellicott 1887
- Opercularia hydrachinidarum Faure-Fremiet 1905
- Opercularia irritabilis Kempel ?
- Opercularia lichtensteini Stein 1868
- Opercularia medians Collin 1909
- Opercularia microdiscus Faure-Fremiet 1904
- Opercularia microstoma Stein 1868
- Opercularia minima Kahl 1935
- Opercularia protecta Penard 1922
- Opercularia plicatilis Stokes 1884
- Opercularia rugosa Kellicott 1884
- Opercularia stenostoma Stein 1854
- Opercularia venusta Foissner 1979
- Opercularia vestita Stokes 1887
- Opercularia wallengreni Grier ?
- Opercularia zschokkei Keiser 1921
- Operculariella parasitica Stammer 1948
- Operculigera asymmetrica Clamp 1991
- Operculigera insolita Clamp 1991
- Operculigera montanea Kane 1969
- Operculigera opstipa Clamp 1991
- Operculigera seticola Clamp 1991
- Operculigera taura Clamp 1991
- Ophiurephelota tenax Jankowski 1981
- Ophiodiscus wetzeli Lust 1950
- Ophiuraespira weilli Chatton & Lwoff 1930
- Ophionella picta Kellicott 1884
- Ophrydium adae Evarts 1880
- Ophisthostomum bengalensis Ghosh 1928
- Ophrydium boreale Penard 1922
- Ophrydium eichhorni Ehrenberg 1838
- Ophrydium crassicaule Penard 1922
- Ophrydium fixa D'Udekem 1862
- Ostracodinium mysorei -> LB0002: 49
- Ostracodinium rugoloricatum -> LB0002: 49
- Ostracodinium stokyi -> LB0002: 49
- Ostracodinium nanum -> LB0002: 49
- Ostracodinium tenue -> LB0002: 49
- Ostracodinium tiete -> LB0002: 49
- Ostracodinium trivesiculatum -> LB0002: 49
- Ostracodinium venustum -> LB0002: 49
- Ovalorhabdos sapropelica Foissner 1984
- Ovolembus caroni Small & Lynn 1985
- Oxychona multifida Jankowski 1973
- Oxychona suprema Jankowski 1973
- Oxychonina multifida Corliss 1979
- Oxytricha aeruginosa Wrzesniowski 1870
- Oxytricha acuminata Stokes 1887