Camaena obtecta (H. Fischer, 1898)
Baudinella occidentalis F. Köhler, 2011 Australia, Jungulu Island
Mouldingia occidentalis G.A. Solem, 1984 Western Australia10 mm
Nipponochloritis occidentalis M. Azuma, 1982 Japan
Camaena ochthoplax (W.H. Benson, 1860)
Sphaerospira oconnellensis J.C. Cox, 1871 Australia, Mackay25 mm
Ningbingia octava G.A. Solem, 1981 Australia, Ningbing Ranges15 mm
Papuina odilia W.S.S. Van Benthem-Jutting, 1965 Indo-Pacific
Papuanella ogeramuensis (W. Kobelt, 1914) Papua New Guinea23,7 mm
Satsuma okiensis H.A. Pilsbry & Y. Hirase,1908 Japan, Shimane26,3 mm
Basedowena olgana G.A. Solem, 1993 Northern Territory
Pleuroxia oligopleura R. Tate, 1894 Australia, Eucla14 mm
Pleuroxia oligopleura numba T. Iredale, 1939 Western Australia
Ganesella omeiensis H.A. Pilsbry & T.C. Yen China, Sichuan15,5 mm
Satsuma omoro H. Minato, 1982 Japan
Satsuma omphalodes H.A. Pilsbry, 1901 Japan, Hyogo
Landouria omphalostoma B. Páll-Gergely& A. Hunyadi, 2013 Yunnan, China
Camaena onae Thach, 2016
Ganesella onestera (J.F. Mabille, 1887) Vietnam, Tonkin15 mm
Turgenitubulus opiranus G.A. Solem, 1981 Ningbing Ranges
Ganesella optima H.A. Pilsbry, 1902
Labyrinthus oreas F.C.L. Koch, 1844 Ecuador
Nanotrachia orientalis (G.A. Solem, 1984) Western Australia
Westraltrachia oscarensis (J.C. Cox, 1892) Western Australia
Nipponochloritis oscitans (E.C. Von Martens, 1881) Japan, Toga Oga
Nipponochloritis oscitans kiyosumiensis M. Azuma, 1982 Japan
Satsuma oshimae H.A. Pilsbry, 1901 Japan28,4 mm
Amplirhagada osmondi G.A. Solem, 1988 Western Australia, Kimberley
Nipponochloritis osumiensis (H.A. Pilsbry& Y. Hirase, 1904) Japan, Kagoshima
Labyrinthus otis (J. Lightfoot, 1786) Panama52 mm
Labyrinthus otis orthorinus H.A. Pilsbry, 1899 Panama48 mm
Pleuroxia overlanderensis G.A. Solem, 1997 Western Australia17 mm
Ganesella oxytropis (O.F. von Möllendorff,1901) Vietnam, Tonkin
Camaena pachychila (E.A. Smith, 1893) Vietnam, Tonkin43 mm
Xanthomelon pachystylum (L. Pfeiffer, 1845) Australia, Dingo Beach43,7 mm