- orobaena, Drymaeus orobaena (A.V.M.D. D'Orbigny, 1835) - (BULIMULIDAE)
- orobia, Achatina orobia W.H. Benson, 1856 - syn of: Glessula orobia (W.H. Benson, 1856) - (ACHATINIDAE)
- orobia, Oxytesta orobia W.H. Benson, 1848 - syn of: Oxytesta orubia (W.H. Benson, 1848) - (ARIOPHANTIDAE)
- Orobia, syn of: Genus Macrochlamys W.H. Benson, 1832 in J.E. Gray, 1847 (ARIOPHANTIDAE)
- orobia, Buliminus sindicus orobia C.M.F. Ancey, 1893 - (ENIDAE)
- orobia, Glessula orobia (W.H. Benson, 1856) - (SUBULINIDAE)
- Orobitella, Genus Orobitella W.H. Dall, 1900 (LASAEIDAE)
- Orobophana, Genus Orobophana A. Wagner, 1905 (HELICINIDAE)
- orocopia, Eremarionta orocopia G. Willett, 1939 - (HELMINTHOGLYPTIDAE)
- Orodoris, syn of: Genus Miamira L.S.R. Bergh, 1874 (CHROMODORIDIDAE)
- Orodrymaeus, Subgenus Drymaeus (Orodrymaeus) H.A. Pilsbry, 1926 (BULIMULIDAE)
- orokau, Leiorhagium orokau M. Haase & P. Bouchet, 1998 - (HYDROBIIDAE)
- orolgainica, Gonamella orolgainica H. Zhegallo, 1996 † - syn of: Protoconus orolgainicus H. Zhegallo, 1996 † - (CARINOPELTIDAE) (FOSSIL)
- orolgainicus, Protoconus orolgainicus H. Zhegallo, 1996 † - (CARINOPELTIDAE) (FOSSIL)
- orolibas, Fontigens orolibas L.R. Hubricht, 1957 - (AMNICOLIDAE)
- oromii, Insulivitrina oromii (C.M. Ibáñez & M.R. Alonso, 1988) - (VITRINIDAE)
- oronensis, Lewyites oronensis (Lewy, 1969 †) - (DIPLOMOCERATIDAE) (FOSSIL)
- oronensis, Stagnicola oronensis F.C. Baker, 1904 - syn of: Stagnicola oronoensis F.C. Baker, 1904 - (LYMNAEIDAE)
- oronocensis, Pomacea oronocensis L.A. Reeve - syn of: Pomacea glauca (C. Linnaeus, 1758) - (AMPULLARIIDAE)
- oronoensis, Stagnicola oronoensis F.C. Baker, 1904 - (LYMNAEIDAE)
- Oronthea, syn of: Genus Kellia W.H. Turton, 1822 (KELLIIDAE)
- orontis, Melanopsis orontis P.M. Pallary, 1939 - (MELANOPSIDAE)
- oropaensis, Mediterranea oropaensis C.A. Westerlund, 1886 - syn of: Mediterranea polygyrus (C. Pollonera, 1885) - (OXYCHILIDAE)
- oropendula, Caryocorbula oropendula A.A. Olsson, 1922 † - (CORBULIDAE) (FOSSIL)
- oropendula dolicha, Caryocorbula oropendula dolicha W.P. Woodring, 1982 - (CORBULIDAE)
- oropendula stena, Caryocorbula oropendula stena W.P. Woodring, 1982 - (CORBULIDAE)
- orophila, Clausilia orophila J.R. Bourguignat, 1877 - syn of: Clausilia bidentata abietina (D. Dupuy, 1850) - (CLAUSILIIDAE)
- orophila, Epiphragmophora orophila C.M.F. Ancey, 1903 - (EPIPHRAGMOPHORIDAE)
- orophila, Melanopsis orophila P.M. Pallary, 1920 - (MELANOPSIDAE)
- orophila, Glessula orophila (L.A. Reeve, 1849) - (SUBULINIDAE)
- orophila, Succinea casta orophila C.M.F. Ancey, 1904 - (SUCCINEIDAE)
- orophilus, Bostryx orophilus P.M.A. Morelet, 1863 - (BULIMULIDAE)
- orophilus, Leptopomoides orophilus (W.H. Benson, 1853) - (CYCLOPHORIDAE)
- orophoma, Mangelia orophoma J.C. Melvill & R. Standen, 1896 - (MANGELIIDAE)
- oroposi, Melanopsis oroposi Papp, 1979 † - (MELANOPSIDAE) (FOSSIL)
- oroposi minoriformis, Melanopsis oroposi minoriformis Papp, 1979 † - (MELANOPSIDAE) (FOSSIL)
- oropuchensis, Brachypodella oropuchensis G.C. Spence - (UROCOPTIDAE)
- oros, Calliotropis oros C. Vilvens, 2007 - (CALLIOTROPIDAE)
- oros marquisensis, Calliotropis oros marquisensis C. Vilvens, 2007 - (CALLIOTROPIDAE)
- orosciana, Guppya gundlachi orosciana E.C. Von Martens, 1892 - (EUCONULIDAE)
- orosi, Caryocorbula orosi A.A. Olsson, 1922 † - (CORBULIDAE) (FOSSIL)
- orosminus, Dolomena dilatata orosminus (P.L. Duclos, 1844) - (STROMBIDAE)
- orospatia, Brookula orospatia C.F. Laseron, 1954 - syn of: Brookula angeli (J.E. Tenison-Woods, 1877) - (SEGUENZIOIDEA (unassigned))
- Orospira, Genus Orospira Butts, 1926 (RAPHISTOMATIDAE) (FOSSIL)
- orotavana, Xerotricha orotavana A. Mousson, 1872 - syn of: Xerotricha orbignii (A.V.M.D. D'Orbigny, 1836) - (HYGROMIIDAE)
- orotis, Chrysallis aspersa orotis W.J. Clench & S. Archer, 1933 - (BRADYBAENIDAE)
- orotis, Pristiloma orotis S.S. Berry, 1930 - (PRISTILOMATIDAE)
- orotundum, Buccinum orotundum W.H. Dall, 1907 - syn of: Buccinum polare J.E. Gray, 1839 - (BUCCINIDAE)
- orovillensis, Nerita orovillensis R.L. Squires & Saul, 2005 † - (NERITIDAE) (FOSSIL)
- oroyensis, Epiphragmophora oroyensis H.A. Pilsbry, 1926 - (EPIPHRAGMOPHORIDAE)
- orozcoae, Volvarina orozcoae J.A. Ortea, 2014 - (MARGINELLIDAE)
- Orphaicus, syn of: Genus Thaumastus J.A. Albers, 1860 (MEGASPIRIDAE)
- orphana, Fluvidona orphana W.B. Miller, W.F. Ponder & K.B. Clark, 1999 - (HYDROBIIDAE)
- orphanensis, Melanella orphanensis A.H. Clarke, 1974 - (EULIMIDAE)
- Orphanopusia, Genus Orphanopusia Fedosov, Herrmann & Bouchet, 2017 (COSTELLARIIDAE)
- orphanta, Alcithoe orphanta T.A. Darragh, 1989 † - (VOLUTIDAE) (FOSSIL)
- orphanuli, Euphaedusa aculus orphanuli (P.M. Heude, 1882) - (CLAUSILIIDAE)
- orphanus, Yochelsonellis orphanus (J. Perner, 1903 †) - (CYRTOLITIDAE) (FOSSIL)
- orpheus, Fusus orpheus A.A. Gould, 1849 - syn of: Trophonopsis orpheus (A.A. Gould, 1849) - (FASCIOLARIIDAE)
- orpheus, Trophonopsis orpheus (A.A. Gould, 1849) - (MURICIDAE)
- orphia, Columbella orphia P.L. Duclos, 1846 - syn of: Mitrella dichroa (G.B. I Sowerby, 1844) - (COLUMBELLIDAE)
- orphia, Mitrella orphia P.L. Duclos in J.C. Chenu, 1846 - syn of: Mitrella dichroa (G.B. I Sowerby, 1844) - (COLUMBELLIDAE)
- Orphnus, syn of: Genus Thaumastus J.A. Albers, 1860 (MEGASPIRIDAE)
- orphyne, Floripatella orphyne (Billings, 1865 †) - (ARCHINACELLIDAE) (FOSSIL)
- Orpiella, Genus Orpiella J.E. Gray, 1855 (HELICARIONIDAE)
- orrae, Canarium urceus orrae R.T. Abbott, 1960 - (STROMBIDAE)
- orri, Conus orri T. Ninomiya & A.J. Da Motta, 1982 - syn of: Lautoconus mercator (C. Linnaeus, 1758) - (CONIDAE)
- orri, Attiliosa orri (W.O. Cernohorsky, 1976) - (MURICIDAE)
- Orrmaesia, Genus Orrmaesia R.N. Kilburn, 1988 (DRILLIIDAE)
- orsae, Mytilarca orsae Isberg, 1934 † - (AMBONYCHIIDAE) (FOSSIL)
- orsae, Cyrtodonta orsae Isberg, 1934 † - (CYRTODONTIDAE) (FOSSIL)
- orsae, Myalina orsae Isberg, 1934 † - (MYALINIDAE) (FOSSIL)
- Orsiniana, syn of: Genus Monacha L.I. Fitzinger, 1833 (HYGROMIIDAE)
- orsinii, Felimare orsinii (J.B. Vérany, 1846) - (CHROMODORIDIDAE)
- orsinii, Glossodoris orsinii J.B. Vérany, 1846 - syn of: Felimare orsinii (J.B. Vérany, 1846) - (CHROMODORIDIDAE)
- orsinii, Hypselodoris orsinii J.B. Vérany, 1846 - syn of: Felimare orsinii (J.B. Vérany, 1846) - (CHROMODORIDIDAE)
- orsinii, Doris orsinii J.B. Vérany, 1846 - syn of: Felimare orsinii (J.B. Vérany, 1846) - (DORIDIDAE)
- orsinii, Pseudamnicola orsinii (H.C. Küster, 1852) - (HYDROBIIDAE)
- orsinii, Monacha orsinii (C. Porro, 1841) - (HYGROMIIDAE)
- orsinii, Theodoxus orsinii E.C. Von Martens, 1879 - syn of: Theodoxus fluviatilis (C. Linnaeus, 1758) - (NERITIDAE)
- orstedi, Columbella orstedi E.C. Von Martens, 1897 - syn of: Anachis moesta (C.B. Adams, 1852) - (COLUMBELLIDAE)
- orstedi, Pachychilus orstedi (O.A.L. Mörch, 1860) - (PACHYCHILIDAE)
- orstedi, Melania orstedi O.A.L. Mörch, 1860 - syn of: Pachychilus orstedi (O.A.L. Mörch, 1860) - (THIARIDAE)
- orstedi planensis, Pachychilus orstedi planensis (I. Lea, 1858) - (PACHYCHILIDAE)
- orstomi, Halgerda orstomi S.J. Fahey & T.M. Gosliner, 2000 - (DISCODORIDIDAE)
- orstomi, Hypermastus orstomi A. Warén, 1994 - (EULIMIDAE)
- orstomi, Marginella orstomi H.E. Coomans, 1975 - (MARGINELLIDAE)
- orstomi, Ledella orstomi (R. von Cosel, 1995) - (NUCULANIDAE)
- orstomi, Phyllidia orstomi Á. Valdés, 2001 - (PHYLLIDIIDAE)
- orstomi, Spondylus orstomi K.L. Lamprell & J.M. Healy, 2001 - (SPONDYLIDAE)
- orstomi, Gastrana orstomi R. von Cosel, 1995 - (TELLINIDAE)
- orstomi, Yoldiella orstomi R. von Cosel, 1995 - syn of: Ledella orstomi (R. von Cosel, 1995) - (YOLDIIDAE)
- orsus, Ataphrus orsus (J.F. Blake, 1905 †) - (ATAPHRIDAE) (FOSSIL)
- orta, Ambigua saxetana orta (M. Paulucci, 1886) - (HELICIDAE)
- Ortalichus, syn of: Genus Orthalicus H.H. Beck, 1837 (ORTHALICIDAE)
- orteai, Cyerce orteai Á. Valdés & Y. Camacho-García, 2000 - (CALIPHYLLIDAE)
- orteai, Trapania orteai J.C. García-Gómez & J.L. Cervera, 1989 - (GONIODORIDIDAE)
- orteai, Haminoea orteai F.F. Talavera, Murillo & J. Templado, 1987 - (HAMINOEIDAE)
- orteai, Crisilla orteai J. Templado & E. Rolán, 1994 - (RISSOIDAE)
- orteai, Triphora orteai J. Espinosa, 2001 - syn of: Triphora ellyae D. De Jong & H.E. Coomans, 1988 - (TRIPHORIDAE)
- orthacantha, Melongena orthacantha H.A. Pilsbry & Johnson, 1917 † - (MELONGENIDAE) (FOSSIL)
- ORTHALICIDAE Martens in Albers, 1860 - Family (GASTROPODA-HETEROBRANCHIA [Subclass]-PULMONATA [Infraclass]-STYLOMMATOPHORA [Order]-ORTHALICOIDEA [Superfamily])
- Orthalicus, Genus Orthalicus H.H. Beck, 1837 (ORTHALICIDAE)
- Orthaliscus, syn of: Genus Sultana R.J. Shuttleworth, 1856 (ORTHALICIDAE)
- Orthalycaeus, syn of: Genus Alycaeus J.E. Gray, 1850 (CYCLOPHORIDAE)
- Orthaspidoceras, Genus Orthaspidoceras Spath, 1925 (STEPHANOCERATIDAE) (FOSSIL)
- Orthaulax, Genus Orthaulax Gabb, 1872 (STROMBIDAE) (FOSSIL)
- orthensis, Pseudolatirus orthensis P. Lozouet, 2015 † - (FASCIOLARIIDAE) (FOSSIL)
- orthezensis, Spaniorinus orthezensis A.E.M. Cossmann & M.A. Peyrot, 1911 † - (GALEOMMATIDAE) (FOSSIL)
- orthezensis, Nassarius orthezensis R. Tournouer, 1876 † - (NASSARIIDAE) (FOSSIL)
- orthezensis, Daphnella orthezensis (Degrange-Touzin, 1894 †) - (RAPHITOMIDAE) (FOSSIL)
- orthezensis, Turritella orthezensis R. Tournouer, 1875 † - (TURRITELLIDAE) (FOSSIL)
- ortheziana, Clio ortheziana É.A. Benoist, 1889 † - (CLIIDAE) (FOSSIL)
- orthii, Caspia orthii S. Clessin & W. Dybowski in W. Dybowski, 1888 - syn of: Pyrgula cincta (H.W. Von Abich, 1859) - (HYDROBIIDAE)
- Orthildaites, Genus Orthildaites Buckman, 1923 (HILDOCERATIDAE) (FOSSIL)
- orthius, Tagelus orthius W.P. Woodring, 1982 † - (SOLECURTIDAE) (FOSSIL)
- Orthocardium, Subgenus Cardium (Orthocardium) Tremlett, 1950 (CARDIIDAE) (FOSSIL)
- Orthoceltites, Genus Orthoceltites Spath , 1951 (DANUBITIDAE) (FOSSIL)
- Orthoceras, Genus Orthoceras Breynius, 1832 (ORTHOCERATIDAE) (FOSSIL)
- orthoceras, Bacillum orthoceras (H.H. Godwin-Austen) - (SUBULINIDAE)
- ORTHOCERATIDAE M'Coy, 1844 - Family (CEPHALOPODA-ORTHOCERATOIDEA [Subclass]-ORTHOCERIDA [Order]) (FOSSIL)
- Orthoceratites, syn of: Genus Orthoceras Breynius, 1832 (ORTHOCERATIDAE) (FOSSIL)
- ORTHOCERIDA (UNASSIGNED) - Family (CEPHALOPODA-ORTHOCERATOIDEA [Subclass]-ORTHOCERIDA [Order]) (FOSSIL)
- ORTHOCERIDAE - syn of Family: ORTHOCERATIDAE (FOSSIL)
- Orthoceros, syn of: Genus Orthoceras Breynius, 1832 (ORTHOCERATIDAE) (FOSSIL)
- ORTHOCEROTIDAE - syn of Family: ORTHOCERATIDAE (FOSSIL)
- orthocheila, Trachia orthocheila C.M.F. Ancey, 1898 - syn of: Westraltrachia derbyi (J.C. Cox, 1892) - (CAMAENIDAE)
- Orthochetus, Genus Orthochetus A.E.M. Cossmann, 1889 (CERITHIIDAE) (FOSSIL)
- orthochila, Styliferina orthochila A. Adams, 1860 - (LITIOPIDAE)
- Orthochilus, Genus Orthochilus A.E.M. Cossmann, 1889 (PLANAXIDAE)
- Orthoclymenia, syn of: Genus Clymenia Mόnster, 1834 (CLYMENIIDAE) (FOSSIL)
- orthoconcavus, Modiolopsis orthoconcavus Fisher, 1957 † - (MODIOMORPHIDAE) (FOSSIL)
- Orthoconus, Genus Orthoconus Stinchcomb , 1986 (HYPSELOCONIDAE) (FOSSIL)
- orthocosta, Promathildia orthocosta (F. Schröder, 1995 †) - (GORDENELLIDAE) (FOSSIL)
- orthocosta, Mathilda orthocosta F. Schröder, 1995 † - syn of: Promathildia orthocosta (F. Schröder, 1995 †) - (MATHILDIDAE) (FOSSIL)
- orthocostae, Turbonilla orthocostae A. Peñas & E. Rolán, 2010 - (PYRAMIDELLIDAE)
- orthocostatum, Gzheloceras orthocostatum (N.D. Kruglov, 1939 †) - (GZHELOCERATIDAE) (FOSSIL)
- orthocostatum, Pleuronautilus orthocostatum N.D. Kruglov, 1939 † - syn of: Gzheloceras orthocostatum (N.D. Kruglov, 1939 †) - (TAINOCERATIDAE) (FOSSIL)
- Orthocycloceras, Genus Orthocycloceras Barskov, 1972 (ORTHOCERATIDAE) (FOSSIL)
- Orthodactylites, Subgenus Dactylioceras (Orthodactylites) Buckman, 1926 (DACTYLIOCERATIDAE) (FOSSIL)
- Orthodesma, Genus Orthodesma Hall & Whitfield, 1875 (MODIOMORPHIDAE) (FOSSIL)
- Orthodochmioceras, Genus Orthodochmioceras Chen, 1981 (CEPHALOPODA (UNASSIGNED)) (FOSSIL)
- orthodonta, Corbicula leana orthodonta H.A. Pilsbry, 1907 - (CYRENIDAE)
- orthodonta, Palaeomutela orthodonta Amalitsky, 1892 † - (PALAEOMUTELIDAE) (FOSSIL)
- orthodoxus, Bulimulus orthodoxus H. Drouët, 1859 - (BULIMULIDAE)
- orthodoxus, Saxurinator orthodoxus H. Schütt, 1960 - (HYDROBIIDAE)
- Orthogarantiana, Subgenus Garantiana (Orthogarantiana) Bentz, 1928 (PARKINSONIIDAE) (FOSSIL)
- orthogaster, Wissenbachia orthogaster C.L.F. von Sandberger † - (BREVICOCERATIDAE) (FOSSIL)
- Orthogibbus, syn of: Genus Gonospira W.J. Swainson, 1840 (STREPTAXIDAE)
- orthogonale, Plesiodiceras orthogonale Pchelintsev, 1959 † - (EPIDICERATIDAE) (FOSSIL)
- orthogonalis, Mactra orthogonalis Dufour, 1881 † - (MACTRIDAE) (FOSSIL)
- orthogonium, Metacoceras orthogonium Ruzhentsev & Shimanskiy, 1954 † - (TAINOCERATIDAE) (FOSSIL)
- Orthomesus, Subgenus Tricolia (Orthomesus) H.A. Pilsbry, 1888 (PHASIANELLIDAE)
- orthomorpha, Pseudocardium orthomorpha Grant & H.R. Gale, 1931 † - (MACTRIDAE) (FOSSIL)
- Orthomyalina, Genus Orthomyalina Newell, 1942 (MYALINIDAE) (FOSSIL)
- Orthonaiadites, Genus Orthonaiadites Khalfin, 1950 (PROKOPIEVSKIIDAE) (FOSSIL)
- Orthonema, Genus Orthonema Meek & Worthen, 1862 (ORTHONEMATIDAE) (FOSSIL)
- ORTHONEMATIDAE Nόtzel & Bandel, 2000 - Family (GASTROPODA-CAENOGASTROPODA [Subclass]-PALAEOSTYLOIDEA [Superfamily]) (FOSSIL)
- ORTHONEMIDAE Nόtzel & Bandel, 2000 - Family (GASTROPODA-CAENOGASTROPODA [Subclass]-CERITHIMORPHA [Order]) (FOSSIL)
- orthonota, Septimyalina orthonota (Mather, 1915 †) - (MYALINIDAE) (FOSSIL)
- Orthonota, Genus Orthonota Conrad, 1841 (ORTHONOTIDAE) (FOSSIL)
- Orthonotella, syn of: Genus Modiolopsis Hall, 1847 (MODIOMORPHIDAE) (FOSSIL)
- ORTHONOTIDAE S.A. Miller, 1877 - Family (BIVALVIA-HETERODONTA [Subclass]-EUHETERODONTA [Infraclass]-SOLENIDA [Order]-ORTHONOTOIDEA [Superfamily]) (FOSSIL)
- orthonotum, Cymatonota orthonotum F.B. Meek & A.H. Worthen † - (MODIOMORPHIDAE) (FOSSIL)
- orthonotum, Endodesma orthonotum F.B. Meek & A.H. Worthen † - syn of: Cymatonota orthonotum F.B. Meek & A.H. Worthen † - (MODIOMORPHIDAE) (FOSSIL)
- Orthonotus, syn of: Genus Orthonota Conrad, 1841 (ORTHONOTIDAE) (FOSSIL)
- Orthonybyoceras, Genus Orthonybyoceras Shimizu & Obata, 1935 (PROTEOCERATIDAE) (FOSSIL)
- Orthonychia, Genus Orthonychia Hall, 1843 (ORTHONYCHIIDAE) (FOSSIL)
- ORTHONYCHIIDAE Bandel & Frύda, 1999 - Family (GASTROPODA-NERITIMORPHA [Subclass]-CYRTONERITIMORPHA [Order]) (FOSSIL)
- Orthonymus, syn of: Genus Theliderma W.J. Swainson, 1840 (UNIONIDAE)
- orthophyes, Melanella orthophyes (R. Sturany, 1903) - (EULIMIDAE)
- orthopleura, Medora dalmatina orthopleura (C.A. Westerlund, 1878) - (CLAUSILIIDAE)
- orthopleura, Makiyamaia orthopleura (R.N. Kilburn, 1983) - (CLAVATULIDAE)
- orthopleura, Melanella orthopleura R. Tate, 1898 - syn of: Melanella augur (G.F. Angas, 1865) - (EULIMIDAE)
- orthopleura, Eulima orthopleura R. Tate, 1898 - syn of: Melanella augur (G.F. Angas, 1865) - (EULIMIDAE)
- orthopleura, Turris orthopleura R.N. Kilburn, 1983 - syn of: Makiyamaia orthopleura (R.N. Kilburn, 1983) - (TURRIDAE)
- orthoplicatula, Turbonilla orthoplicatula S. Nomura, 1936 - (PYRAMIDELLIDAE)
- orthoplicatulata, Turbonilla orthoplicatulata (S. Nomura, 1936) - (PYRAMIDELLIDAE)
- orthoplicatulata, Chemnitzia orthoplicatulata S. Nomura, 1936 - syn of: Turbonilla orthoplicatulata (S. Nomura, 1936) - (PYRAMIDELLIDAE)
- Orthopnoea, syn of: Genus Phasianella J.B.P.A. Lamarck, 1804 (PHASIANELLIDAE)
- Orthopoma, Subgenus Septaria (Orthopoma) J.E. Gray, 1867 (NERITIDAE)
- orthoptalmus, Pterotrachea orthoptalmus J.J. Tesch, 1906 - syn of: Pterotrachea hippocampus R.A. Philippi, 1836 - (PTEROTRACHEIDAE)
- Orthoptychus, Genus Orthoptychus Futterer, 1892 (CAPRINIDAE) (FOSSIL)
- orthoptyx, Thaumatoptyx orthoptyx H. Nordsieck, 2003 - (CLAUSILIIDAE)
- Orthoptyxis, Genus Orthoptyxis Yang & Wang, 1985 (CEPHALASPIDA (UNASSIGNED)) (FOSSIL)
- orthorinus, Labyrinthus otis orthorinus H.A. Pilsbry, 1899 - (CAMAENIDAE)
- Orthorizoceras, Genus Orthorizoceras Krφger , 2008 (ONCOCERATIDAE) (FOSSIL)
- orthoseptatum, Triendoceras orthoseptatum Flower, 1958 † - (ENDOCERATIDAE) (FOSSIL)
- Orthosphinctes, Genus Orthosphinctes Schindewolf , 1925 (ATAXIOCERATIDAE) (FOSSIL)
- Orthospira, Genus Orthospira Kutassy, 1940 (COELOSTYLINIDAE) (FOSSIL)
- orthostoma, Platyla orthostoma (M. Jackiewicz, 1979) - (ACICULIDAE)
- orthostoma, Drymaeus orthostoma E.A. Smith, 1877 - (BULIMULIDAE)
- orthostoma, Granaria orthostoma C. Piersanti, 1927 - syn of: Granaria variabilis (J.P.R. Draparnaud, 1801) - (CHONDRINIDAE)
- orthostoma, Paracochlodina orthostoma (K.T. Menke, 1830) - (CLAUSILIIDAE)
- orthostoma, Inozonites orthostoma (L. Pfeiffer, 1845) - (HELICARIONIDAE)
- Orthostoma, Genus Orthostoma Conrad, 1838 (OPHILETIDAE) (FOSSIL)
- orthostoma, Praenatica orthostoma (Barrois, 1889 †) - (PLATYCERATIDAE) (FOSSIL)
- orthostoma, Turbo orthostoma E.A.L. Kittl, 1894 † - (TURBINIDAE) (FOSSIL)
- orthostoma filiformis, Paracochlodina orthostoma filiformis (E.A. Bielz, 1861) - (CLAUSILIIDAE)
- Orthostomia, Subgenus Undularia (Orthostomia) Stoppani, 1858 (PROTORCULIDAE) (FOSSIL)
- Orthostylus, syn of: Genus Helicostyla A.E.J. Fιrussac, 1821 (BRADYBAENIDAE)
- Orthosurcula, Genus Orthosurcula Casey, 1904 (COCHLESPIRIDAE) (FOSSIL)
- orthosymmetrica, Turritella orthosymmetrica S.S. Berry, 1953 - (TURRITELLIDAE)
- Orthotheca, Genus Orthotheca Cowper Reed, 1909 (CIRCOTHECIDAE) (FOSSIL)
- orthotheca, Clio orthotheca (J.J. Tesch, 1948) - (CLIIDAE)
- ORTHOTHECIDAE Sysoev, 1957 - Family (HYOLITHA-ORTHOTHECIDA [Order]) (FOSSIL)
- Orthotomium, syn of: Genus Rabdotus J.A. Albers, 1850 (BULIMULIDAE)
- Orthotrigonia, Genus Orthotrigonia Cox, 1952 (MYOPHORELLIDAE) (FOSSIL)
- Orthoyoldia, Genus Orthoyoldia A.E. Verrill & K.J. Bush, 1897 (YOLDIIDAE)
- orthra, Pleiorytis orthra W.P. Woodring, 1982 † - (VENERIDAE) (FOSSIL)
- orthria, Mulinia orthria Gardner 1928 † - (MACTRIDAE) (FOSSIL)
- Orthriochiton, Genus Orthriochiton Vendrasco & Runnegar, 2004 (PREACANTHOCHITONIDAE) (FOSSIL)
- orthrius, Tagelus orthrius Woodring 1982 † - (SOLECURTIDAE) (FOSSIL)
- ORTHROZANCLIDAE Conway Morris & Caron, 2007 - Family (DIPLACOPHORA-SACHITIDA [Order]) (FOSSIL)
- Orthrozanclus, Genus Orthrozanclus Conway Morris & Caron, 2007 (ORTHROZANCLIDAE) (FOSSIL)
- orthus, Orthildaites orthus Buckman, 1923 † - syn of: Orthildaites douvillei (Haug, 1884 †) - (HILDOCERATIDAE) (FOSSIL)
- ortigia, Columbella ortigia P.L. Duclos, 1848 - (COLUMBELLIDAE)
- ortiguilla, Collisella ortiguilla R. Ramírez, 1974 - syn of: Scurria ceciliana (A.V.M.D. D'Orbigny, 1841) - (LOTTIIDAE)
- ortispuenti, Scutalus ortispuenti W.K. Weyrauch, 1967 - syn of: Scutalus ortizpuentei W.K. Weyrauch, 1967 - (BULIMULIDAE)
- ortivus, Retites ortivus Ruzhencev & Bogoslovskaya, 1978 † - (RETICULOCERATIDAE) (FOSSIL)
- ortizae, Eulimella ortizae A. Peñas & E. Rolán, 2000 - (PYRAMIDELLIDAE)
- ortizi, Aegires ortizi J. Templado, A.A. Luque & J.A. Ortea, 1987 - (AEGIRIDAE)
- ortizi, Bostryx ortizi W.K. Weyrauch, 1967 - (BULIMULIDAE)
- ortizi, Iberus marmoratus ortizi E. Garcia San Nicolás, 1957 - (HELICIDAE)
- ortizi, Amandana cisternasi ortizi (L. Gasull, 1964) - (HYGROMIIDAE)
- ortizi, Haplocochlias ortizi J. Espinosa, J.A. Ortea & R. Fernández-Garcés, 2005 - (SKENEIDAE)
- ortizi, Oestophora ortizi A.J. de Winter & T.E.J. Ripken, 1991 - (TRISSEXODONTIDAE)
- ortizianus, Thaumastus ortizianus F. Haas, 1955 - (MEGASPIRIDAE)
- Ortizius, Subgenus Oxychilus (Ortizius) L. Forcart, 1957 (OXYCHILIDAE)
- ortizpuentei, Scutalus ortizpuentei W.K. Weyrauch, 1967 - (BULIMULIDAE)
- ortmanni, Lucina ortmanni H.F.A. von Ihering, 1899 † - (LUCINIDAE) (FOSSIL)
- ortmanni, Neilo ornata ortmanni Erdmann & Morra, 1985 - (MALLETIIDAE)
- ortmanni, Polinices ortmanni H.F.A. von Ihering, 1907 † - (NATICIDAE) (FOSSIL)
- ortmanni, Villosa ortmanni (B. Walker, 1925) - (UNIONIDAE)
- ortmanni, Pseudospatha ortmanni H.A. Pilsbry & J.C. Bequaert, 1927 - syn of: Pseudospatha tanganyicensis (E.A. Smith, 1880) - (UNIONIDAE)
- ortmanni, Pitar ortmanni H.F.A. von Ihering, 1907 - syn of: Pitar patagonicus (A.V.M.D. D'Orbigny, 1842) - (VENERIDAE)
- Ortmanniana, Subgenus Lampsilis (Ortmanniana) Frierson, 1927 (UNIONIDAE)
- ortneri, Purpuriconus ortneri E.J. Petuch, 1998 - (CONIDAE)
- Ortonella, Genus Ortonella Ulrich, 1893 (CYRTODONTIDAE) (FOSSIL)
- ortoni, Ampullina ortoni W.M. Gabb, 1870 † - (AMPULLINIDAE) (FOSSIL)
- ortoni, Strombopoma ortoni (H.A. Pilsbry, 1924) - (COCHLIOPIDAE)
- ortoni, Dyris ortoni (W.M. Gabb, 1869 †) - (COCHLIOPIDAE) (FOSSIL)
- ortoni, Neritina ortoni T.A. Conrad, 1871 † - (NERITIDAE) (FOSSIL)
- ortoni, Orthoceras ortoni F.B. Meek, 1872 † - syn of: Westonoceras ortoni (F.B. Meek, 1872 †) - (ORTHOCERATIDAE) (FOSSIL)
- ortoni, Systrophia ortoni (J.C.H. Crosse, 1871) - (SCOLODONTIDAE)
- ortoni, Westonoceras ortoni (F.B. Meek, 1872 †) - (WESTONOCERATIDAE) (FOSSIL)
- ortoni schindleri, Strombopoma ortoni schindleri W. Blume, 1958 - (COCHLIOPIDAE)
- ortonia, Columbella ortonia P.L. Duclos, 1850 - (COLUMBELLIDAE)
- Ortygia, syn of: Genus Chamelea O.A.L. Mφrch, 1853 (VENERIDAE)
- oruaensis, Neoguraleus oruaensis A.W.B. Powell, 1942 - (MANGELIIDAE)
- oruaensis, Retusa oruaensis (W.H. Webster, 1908) - (RETUSIDAE)
- orubia, Oxytesta orubia (W.H. Benson, 1848) - (ARIOPHANTIDAE)
- oruktus, Chiton oruktus (M.M. Maughan, 1900) - (CHITONIDAE)
- oruktus, Rhyssoplax oruktus M.M. Maughan, 1900 - syn of: Chiton oruktus (M.M. Maughan, 1900) - (CHITONIDAE)
- orulganica, Maitaia orulganica Biakov, 2013 † - (ATOMODESMATIDAE) (FOSSIL)
- orulganica, Myonia orulganica Muromtseva, 1984 † - (VACUNELLIDAE) (FOSSIL)
- Orulganites, Genus Orulganites Ruzhentzev, 1960 (ORULGANITIDAE) (FOSSIL)
- ORULGANITIDAE Ruzhencev, 1965 - Family (CEPHALOPODA-AMMONOIDEA [Subclass]-GONIATITIDA [Order]-SCHISTOCERATOIDEA [Superfamily]) (FOSSIL)
- Orustia, Subgenus Helicostyla (Orustia) O.A.L. Mφrch, 1853 (BRADYBAENIDAE)
- orvikui, Strandoceras orvikui Kröger, 2007 † - (CYRTOGOMPHOCERATIDAE) (FOSSIL)
- orvillensis, Vaugonia orvillensis D.P. Kelly, 1995 † - (MYOPHORELLIDAE) (FOSSIL)
- orycta, Alocospira orycta (R. Tate, 1889 †) - (ANCILLARIIDAE) (FOSSIL)
- orycta, Cylichna orycta (R.B. Watson, 1883) - (CYLICHNIDAE)
- orycta, Zeacuminia orycta (H.H. Suter, 1913 †) - (TEREBRIDAE) (FOSSIL)
- orycta, Negulus orycta C.M. Cooke & H.A. Pilsbry, 1920 - (VERTIGINIDAE)
- orycteropusi, Zuluscaphites orycteropusi Van Hoepen, 1955 † - (LYELLICERATIDAE) (FOSSIL)
- Oryctomya, Genus Oryctomya Dall, 1898 (PSAMMOBIIDAE) (FOSSIL)
- oryctus, Turbo oryctus (H.H. Suter, 1917 †) - (TURBINIDAE) (FOSSIL)
- Orygoceras, Genus Orygoceras Brusina, 1882 (HYDROBIIDAE) (FOSSIL)
- orygoforme, Wardoceras orygoforme Hook & Flower, 1977 † - (MICHELINOCERATIDAE) (FOSSIL)
- orynskii, Coahuilites orynskii Böse, 1928 † - (SPHENODISCIDAE) (FOSSIL)
- orysa, Leptinaria orysa (J.G. Bruguière, 1789) - (SUBULINIDAE)
- orysacea, Oleacina orysacea (P.C.A.S.L. Rang in D'Orbigny, 1842) - (OLEACINIDAE)
- oryx, Dentalium oryx (M. Boissevain, 1906) - (DENTALIIDAE)
- oryx, Entalinopsis oryx M. Boissevain, 1906 - syn of: Dentalium oryx (M. Boissevain, 1906) - (ENTALINIDAE)
- oryx, Orthoceras oryx Whidborne † - (ORTHOCERATIDAE) (FOSSIL)
- oryza, Achatinella oryza L. Pfeiffer - syn of: Leptachatina oryza L. Pfeiffer, 1856 - (ACHATINELLIDAE)
- oryza, Rictaxis oryza W.M. Gabb, 1872 † - (ACTEONIDAE) (FOSSIL)
- oryza, Volvaria oryza J.B.P.A. Lamarck, 1822 - syn of: Gibberula oryza (J.B.P.A. Lamarck, 1822) - (ACTEONIDAE)
- oryza, Leptachatina oryza L. Pfeiffer, 1856 - (AMASTRIDAE)
- oryza, Ancilla oryza L.A. Reeve, 1864 - syn of: Ancilla lineolata (A. Adams, 1853) - (ANCILLARIIDAE)
- oryza, Buccinum oryza R.W. Dunker, 1847 - syn of: Zafrona pulchella (H.M.D. de Blainville, 1829) - (BUCCINIDAE)
- oryza, Bulla oryza J.G. Totten, 1835 - syn of: Cylichnella oryza (J.G. Totten, 1835) - (BULLIDAE)
- oryza, Ittibittium oryza (O.A.L. Mörch, 1876) - (CERITHIIDAE)
- oryza, Bittium oryza O.A.L. Mörch, 1876 - syn of: Ittibittium oryza (O.A.L. Mörch, 1876) - (CERITHIIDAE)
- oryza, Chiton oryza L. Spengler, 1797 - syn of: Stenosemus albus (C. Linnaeus, 1767) - (CHITONIDAE)
- oryza, Retizafra oryza K. Monsecour & D. Monsecour, 2016 - (COLUMBELLIDAE)
- oryza, Anachis oryza R.W. Dunker, 1847 - syn of: Zafrona pulchella (H.M.D. de Blainville, 1829) - (COLUMBELLIDAE)
- oryza, Mitromica oryza G. Rosenberg & R. Salisbury, 2003 - (COSTELLARIIDAE)
- oryza, Pusia oryza H. Turner, 2001 - syn of: Pusia oryzum E.A. Kay, 1979 - (COSTELLARIIDAE)
- oryza, Cylichnella oryza (J.G. Totten, 1835) - (CYLICHNIDAE)
- oryza, Ransoniella oryza L. Dolin, 2007 - syn of: Notadusta punctata (C. Linnaeus, 1771) - (CYPRAEIDAE)
- oryza, Gibberula oryza (J.B.P.A. Lamarck, 1822) - (CYSTISCIDAE)
- oryza, Gibberula oryza Doublier, 1853 - syn of: Gibberula miliaria (C. Linnaeus, 1758) - (CYSTISCIDAE)
- oryza, Amphorella oryza R.T. Lowe, 1852 - (FERUSSACIIDAE)
- oryza, Saccoia oryza Š. Brusina, 1893 † - (HYDROBIIDAE) (FOSSIL)
- oryza, Stenosemus oryza L. Spengler, 1797 - syn of: Stenosemus albus (C. Linnaeus, 1767) - (ISCHNOCHITONIDAE)
- oryza, Eucithara oryza R.B. Hinds, 1843 - syn of: Eucithara oriza (R.B. Hinds, 1843) - (MANGELIIDAE)
- oryza, Olivella oryza P.L. Duclos, 1835 - syn of: Olivella floralia (P.L. Duclos, 1844) - (OLIVELLIDAE)
- oryza, Dentiovula oryza (Y. Omi & P.W. Clover, 2005) - (OVULIDAE)
- oryza, Odostomia oryza A. Garrett, 1873 - (PYRAMIDELLIDAE)
- oryza, Rissoina oryza (A. Garrett, 1873) - (RISSOINIDAE)
- oryza, Tellina oryza R. von Cosel, 1995 - (TELLINIDAE)
- oryza, Melania oryza E. Sismonda, 1842 † - syn of: Saccoia oryza Š. Brusina, 1893 † - (THIARIDAE) (FOSSIL)
- oryza, Trivirostra oryza (J.B.P.A. Lamarck, 1810) - (TRIVIIDAE)
- oryza, Trivia oryza J.B.P.A. Lamarck, 1810 - syn of: Trivirostra oryza (J.B.P.A. Lamarck, 1810) - (TRIVIIDAE)
- oryza, Voluta oryza A. da Costa, 1829 - syn of: Ringicula auriculata (M. Ménard De La Groye, 1811) - (VOLUTIDAE)
- oryza, Zebina oryza (A. Garrett, 1873) - syn of: Rissoina oryza (A. Garrett, 1873) - (ZEBINIDAE)
- oryza avus, Leptachatina oryza avus H.A. Pilsbry & C.M. Cooke, 1914 - (AMASTRIDAE)
- oryza hesperia, Leptachatina oryza hesperia H.A. Pilsbry & C.M. Cooke, 1914 - (AMASTRIDAE)
- oryza minor, Gibberula oryza minor P.M. Pallary, 1920 - syn of: Gibberula oryza (J.B.P.A. Lamarck, 1822) - (CYSTISCIDAE)
- oryza subcylindracea, Leptachatina oryza subcylindracea C.M. Cooke, 1910 - (AMASTRIDAE)
- oryza triticum, Trivirostra oryza triticum F.A. Schilder, 1932 - syn of: Trivirostra triticum F.A. Schilder, 1932 - (TRIVIIDAE)
- oryza turneri, Trivirostra oryza turneri F.A. Schilder, 1932 - syn of: Trivirostra turneri F.A. Schilder, 1932 - (TRIVIIDAE)
- oryzaeformis, Purpuradusta oryzaeformis F.Jr. Lorenz & G.H.W. Sterba, 1999 - (CYPRAEIDAE)
- oryzaeformis, Thecodonta oryzaeformis (J.T. Kuroda & T. Habe, 1971) - (MONTACUTIDAE)
- oryzaella, Acteocina oryzaella T. Habe, 1956 - syn of: Truncacteocina oryzaella (T. Habe, 1956) - (ACTEOCINIDAE)
- oryzaella, Truncacteocina oryzaella (T. Habe, 1956) - (CYLICHNIDAE)
- oryzaformis, Bankia oryzaformis P.B. Sivickis, 1928 - syn of: Bankia carinata (J.E. Gray, 1827) - (TEREDINIDAE)
- oryzagrana, Simnialena oryzagrana L. Dolin, 1991 † - (OVULIDAE) (FOSSIL)
- oryzana, Abida oryzana É.A.A. Locard, 1894 - syn of: Abida secale (J.P.R. Draparnaud, 1801) - (CHONDRINIDAE)
- oryzarum, Nerita oryzarum (C.A. Récluz, 1841) - (NERITIDAE)
- oryzarum, Argonerita oryzarum C.A. Récluz, 1841 - syn of: Nerita oryzarum (C.A. Récluz, 1841) - (NERITIDAE)
- oryzata, Argonauta oryzata F.C. Meuschen, 1787 - syn of: Argonauta nodosa J. Lightfoot, 1786 - (ARGONAUTIDAE)
- oryzatus, Thylacodes oryzatus O.A.L. Mörch, 1862 - (VERMETIDAE)
- Oryzoconcha, syn of: Genus Pojetaia Jell, 1980 (NUCULIDA (UNASSIGNED)) (FOSSIL)
- oryzoidea, Ellatrivia oryzoidea (T. Iredale, 1935) - (TRIVIIDAE)
- oryzoidea, Trivirostra oryzoidea T. Iredale, 1935 - syn of: Ellatrivia oryzoidea (T. Iredale, 1935) - (TRIVIIDAE)
- oryzoides, Mitrella oryzoides Gardner, 1947 † - (COLUMBELLIDAE) (FOSSIL)
- oryzoides, Volvarina oryzoides J. Gardner, 1937 † - (MARGINELLIDAE) (FOSSIL)
- oryzoides, Olivella oryzoides J. Gardner, 1937 † - (OLIVELLIDAE) (FOSSIL)
- Oryzosoma, Genus Oryzosoma H.A. Pilsbry, 1891 (OLEACINIDAE)
- oryzum, Pusia oryzum E.A. Kay, 1979 - (COSTELLARIIDAE)
- orzai, Helicella orzai E. Gittenberger & M.Y. Manga, 1980 - (HYGROMIIDAE)
- orzeskoi, Avenionia orzeskoi E. Caziot, 1910 - syn of: Avenionia brevis (J.P.R. Draparnaud, 1805) - (HYDROBIIDAE)
- orzeskoi, Trochulus orzeskoi E. Caziot - syn of: Trichia hispida (C. Linnaeus, 1758) - (HYGROMIIDAE)
- orzeszkoi, Bythinella orzeszkoi E. Caziot, 1910 - (BYTHINELLIDAE)
- orzolae, Theba orzolae E. Gittenberger & T.E.J. Ripken, 1985 - (HELICIDAE)
- osae, Jorunna osae Y. Camacho-García & T.M. Gosliner, 2008 - (DISCODORIDIDAE)
- osagawai, Buccinum osagawai T. Habe & K. Itô, 1968 - (BUCCINIDAE)
- osagense, Muensteroceras osagense (Swallow, 1860 †) - (MUENSTEROCERATIDAE) (FOSSIL)
- osagense, Catoraphiceras osagense Ulrich & al., 1944 † - (PROTOCYCLOCERATIDAE) (FOSSIL)
- osakaensis, Macoma osakaensis Krishtofovich, 1957 † - (TELLINIDAE) (FOSSIL)
- osakensis, Biplica osakensis T. Kase, 1990 † - (RINGICULIDAE) (FOSSIL)
- osapiensis, Subcancilla osapiensis E.J. Koperberg, 1931 - syn of: Cancilla abyssicola (M.M. Schepman, 1911) - (MITRIDAE)
- osawanoensis, Barbatia osawanoensis Tsuda 1959 † - (ARCIDAE) (FOSSIL)
- osawanoensis, Megacardita osawanoensis K. Tsuda, 1959 † - (CARDITIDAE) (FOSSIL)
- osawanoensis, Cochlespira osawanoensis K. Tsuda, 1959 - (COCHLESPIRIDAE)
- osawanoensis, Anisocorbula osawanoensis K. Tsuda, 1959 † - (CORBULIDAE) (FOSSIL)
- osawanoensis, Nipponocrassatella osawanoensis (Tsuda 1959) † - (CRASSATELLIDAE) (FOSSIL)
- osawanoensis, Leionucula osawanoensis (K. Tsuda, 1959 †) - (NUCULIDAE) (FOSSIL)
- osbeckii, Aegista osbeckii (R.A. Philippi, 1847) - (BRADYBAENIDAE)
- osbeckii, Unio osbeckii R.A. Philippi, 1844 - syn of: Nodularia douglasiae (J.E. Gray in E. Griffith & E. Pidgeon, 1834) - (UNIONIDAE)
- osberti, Choanopomops osberti (H.B. Tristram, 1861) - (POMATIIDAE)
- osbornei, Calliostoma osbornei (A.W.B. Powell, 1926) - (CALLIOSTOMATIDAE)
- osbornei, Maurea osbornei A.W.B. Powell, 1926 - syn of: Calliostoma osbornei (A.W.B. Powell, 1926) - (CALLIOSTOMATIDAE)
- osbornei, Naticopsis osbornei E.K. Yoo, 1988 † - (DELPHINULOPSIDAE) (FOSSIL)
- osborni, Tholachatina osborni (H.A. Pilsbry, 1919) - (ACHATINIDAE)
- osborni, Aesopus osborni L.G. Hertlein & A.M. Strong, 1951 - (COLUMBELLIDAE)
- osborni, Silvigulella osborni H.A. Pilsbry, 1919 - (STREPTAXIDAE)
- osborni, Homorus osborni H.A. Pilsbry, 1919 - (SUBULINIDAE)
- Osbornoceras, Genus Osbornoceras Foerste, 1936 (KAROCERATIDAE) (FOSSIL)
- Oscabrella, syn of: Genus Cryptoplax H.M.D. De Blainville, 1818 (CRYPTOPLACIDAE)
- Oscaniella, syn of: Genus Pleurobranchus G.L.C.F.D. Cuvier, 1804 (PLEUROBRANCHIDAE)
- Oscaniopsis, syn of: Genus Euselenops H.A. Pilsbry, 1896 (PLEUROBRANCHAEIDAE)
- Oscanius, syn of: Genus Pleurobranchus G.L.C.F.D. Cuvier, 1804 (PLEUROBRANCHIDAE)
- Oscarboettgeria, Subgenus Euomphalia (Oscarboettgeria) W.A. Lindholm, 1927 (HYGROMIIDAE)
- oscarensis, Westraltrachia oscarensis (J.C. Cox, 1892) - (CAMAENIDAE)
- oscarensis perca, Westraltrachia oscarensis perca T. Iredale, 1939 - syn of: Westraltrachia oscarensis (J.C. Cox, 1892) - (CAMAENIDAE)
- oscari, Neomenia oscari L. Salvini-Plawén, 2006 - (NEOMENIIDAE)
- oscari, Oxychilus oscari M. von Kimakowicz, 1883 - (OXYCHILIDAE)
- oscari, Unio oscari B.H. Wright, 1892 - syn of: Elliptio jayensis I. Lea, 1838 - (UNIONIDAE)
- oscari, Schistophallus oscari (M. Kimakowicz, 1883) - (ZONITIDAE)
- oscariana, Tyrannophaedusa oscariana H.A. Pilsbry, 1901 - (CLAUSILIIDAE)
- oscariana, Vertigo oscariana V. Sterki, 1890 - (VERTIGINIDAE)
- oscarii, Albinaria schuchii oscarii (O. Böttger, 1883) - (CLAUSILIIDAE)
- oscaritoi, Hyalina oscaritoi J. Espinosa, L. Moro & J.A. Ortea, 2011 - (MARGINELLIDAE)
- Osceanius, syn of: Genus Pleurobranchus G.L.C.F.D. Cuvier, 1804 (PLEUROBRANCHIDAE)
- osceola, Pyruella osceola E.J. Petuch, 1982 † - (BUSYCONIDAE) (FOSSIL)
- osceola, Spirodentalium osceola Walcott, 1890 † - (COLEOLIDAE) (FOSSIL)
- osceolai, Contraconus osceolai E.J. Petuch, 1991 † - syn of: Contraconus adversarius (T.A. Conrad, 1840 †) - (CONIDAE) (FOSSIL)
- osceolai, Terebraspira osceolai E.J. Petuch, 1994 † - (FASCIOLARIIDAE) (FOSSIL)
- oschei, Echinophoria oschei H. Mühlhäusser, 1992 - syn of: Echinophoria wyvillei (R.B. Watson, 1886) - (CASSIDAE)
- oschneri, Tiariturris oschneri (F.M. Anderson & B. Martin, 1914 †) - (PSEUDOMELATOMIDAE) (FOSSIL)
- oschtenica, Hyalinia oschtenica O. Böttger, 1888 - syn of: Longiphallus oschtenicus (O. Böttger, 1888) - (ZONITIDAE)
- oschtenicus, Longiphallus oschtenicus (O. Böttger, 1888) - (OXYCHILIDAE)
- Oscilla, Genus Oscilla A. Adams, 1861 (PYRAMIDELLIDAE)
- oscilla, Gregoia oscilla Fehse, 2017 - (TRIVIIDAE)
- oscillaeformis, Miralda oscillaeformis E. Saurin, 1962 - (PYRAMIDELLIDAE)
- Oscillopha, Genus Oscillopha Malchus, 1990 (OSTREIDAE) (FOSSIL)
- oscitans, Amnicola oscitans H.A. Pilsbry, 1930 - (AMNICOLIDAE)
- oscitans, Tomopleura oscitans R.N. Kilburn, 1986 - (BORSONIIDAE)
- oscitans, Nipponochloritis oscitans (E.C. Von Martens, 1881) - (CAMAENIDAE)
- oscitans, Rhomboidestoma oscitans K. Martin, 1931 † - (CANCELLARIIDAE) (FOSSIL)
- oscitans, Cerithium oscitans G.B. II Sowerby, 1855 - (CERITHIIDAE)
- oscitans, Muticaria macrostoma oscitans (J.G.F. de Charpentier, 1852) - (CLAUSILIIDAE)
- oscitans, Cochlostoma oscitans S. Gofas, 1989 - (COCHLOSTOMATIDAE)
- oscitans, Philine oscitans C. Hedley, 1907 - (PHILINIDAE)
- oscitans, Odostomia oscitans S.L. Lovén, 1846 - syn of: Odostomia ambigua (W.G. Maton & T. Rackett, 1807) - (PYRAMIDELLIDAE)
- oscitans, Turbonilla oscitans S.L. Lovén, 1846 - syn of: Brachystomia eulimoides (S.C.T. Hanley, 1844) - (PYRAMIDELLIDAE)
- oscitans, Rissoina oscitans H.B. Preston, 1905 - syn of: Iravadia delicata (R.A. Philippi, 1849) - (RISSOINIDAE)
- oscitans, Potamopyrgus oscitans T. Iredale, 1944 - (TATEIDAE)
- oscitans, Thapsia oscitans (M. Connolly, 1925) - (UROCYCLIDAE)
- oscitans hitachi, Nipponochloritis oscitans hitachi E. Sorita, 1986 - (CAMAENIDAE)
- oscitans iwatensis, Nipponochloritis oscitans iwatensis E. Sorita, 1986 - (CAMAENIDAE)
- oscitans kiyosumiensis, Nipponochloritis oscitans kiyosumiensis M. Azuma, 1982 - (CAMAENIDAE)
- oscitans shirabuensis, Nipponochloritis oscitans shirabuensis E. Sorita, 1986 - (CAMAENIDAE)
- osclausum, Triphora osclausum E. Rolán & R. Fernández-Garcés, 1995 - (TRIPHORIDAE)
- oscula, Strophiops oscula C.J. Maynard & W.F. Clapp, 1921 - (CERIONIDAE)
- osculans, Isabellaria isabellina osculans (E.C. Von Martens, 1876) - (CLAUSILIIDAE)
- osculans, Costavarix osculans (C.B. Adams, 1850) - (OLEACINIDAE)
- osculans, Phenacolepas osculans (C.B. Adams, 1852) - (PHENACOLEPADIDAE)
- osculans, Costatella osculans (S.S. Haldeman, 1841) - (PHYSIDAE)
- osculans, Hyalosagda osculans (C.B. Adams, 1850) - (SAGDIDAE)
- osculans delaminata, Helix osculans delaminata C.B. Adams, 1851 - syn of: Hyalosagda simplex (H.A. Pilsbry & A.P. Brown, 1910) - (HELICIDAE)
- osculans patzcuarensis, Physa osculans patzcuarensis H.A. Pilsbry, 1891 - syn of: Haitia patzcuarensis (H.A. Pilsbry, 1891) - (PHYSIDAE)
- osculans rhyssa, Physa osculans rhyssa H.A. Pilsbry, 1899 - syn of: Haitia mexicana (R.A. Philippi, 1841) - (PHYSIDAE)
- osculata, Ancilla osculata G.B. III Sowerby, 1900 - syn of: Bullia osculata (G.B. III Sowerby, 1900) - (ANCILLARIIDAE)
- osculata, Bullia osculata (G.B. III Sowerby, 1900) - (NASSARIIDAE)
- osculata, Goniobasis osculata I. Lea, 1872 - (PLEUROCERIDAE)
- osculati, Aylacostoma osculati A. Villa, 1854 - syn of: Aylacostoma maculatum (I. Lea, 1832) - (THIARIDAE)
- Osculigera, Genus Osculigera Kόhn, 1933 (RADIOLITIDAE) (FOSSIL)
- osculum, Gomphoceras osculum Ruedemann, 1916 † - syn of: Phragmocerina osculum (Ruedemann, 1916 †) - (DIESTOCERATIDAE) (FOSSIL)
- osculum, Klikia osculum (Thomä, 1845) † - (HELICIDAE) (FOSSIL)
- osculum, Conradostrea osculum (H.A. Pilsbry & J. Brown, 1927 †) - (OSTREIDAE) (FOSSIL)
- osculum, Phragmocerina osculum (Ruedemann, 1916 †) - (PHRAGMOCERATIDAE) (FOSSIL)
- oscura, Doto oscura C.N.E. Eliot, 1906 - syn of: Doto obscura C.N.E. Eliot, 1906 - (DOTIDAE)
- oselmonta, Anachis oselmonta P.L. Duclos, 1835 - syn of: Anachis freytagi (H. von Maltzan, 1884) - (COLUMBELLIDAE)
- oselmonta, Columbella oselmonta P.L. Duclos, 1840 - syn of: Anachis freytagi (H. von Maltzan, 1884) - (COLUMBELLIDAE)
- oselmonta minima, Zafra oselmonta minima R.P.J. Hervier, 1899 - syn of: Zafra ocellatula (R.P.J. Hervier, 1899) - (COLUMBELLIDAE)
- oselmonta minima, Columbella oselmonta minima R.P.J. Hervier, 1899 - syn of: Zafra ocellatula (R.P.J. Hervier, 1899) - (COLUMBELLIDAE)
- osensis, Biradiolites osensis E. Vidal, 1878 † - (RADIOLITIDAE) (FOSSIL)
- osexiguus, Acteon osexiguus Á. Valdés, 2008 - (ACTEONIDAE)
- oshanovae, Bythiospeum oshanovae (I. Pintér, 1968) - (HYDROBIIDAE)
- oshanovae, Monacha oshanovae I. Pintér & I. Pintér, 1970 - (HYGROMIIDAE)
- oshanovae, Paladilhia oshanovae I. Pintér, 1968 - syn of: Bythiospeum oshanovae (I. Pintér, 1968) - (MOITESSIERIIDAE)
- osheai, Magnoteuthis osheai Braid & K.S. Bolstad, 2015 † - (MASTIGOTEUTHIDAE) (FOSSIL)
- oshikatai, Calliostoma oshikatai T.C. Lan, 1997 - (CALLIOSTOMATIDAE)
- oshikatai, Microstelma oshikatai T.C. Lan, 2003 - (ZEBINIDAE)
- oshimae, Euhadra oshimae (H.A. Pilsbry, 1901) - (BRADYBAENIDAE)
- oshimae, Satsuma oshimae H.A. Pilsbry, 1901 - (CAMAENIDAE)
- oshimae, Luchuphaedusa oshimae (H.A. Pilsbry, 1901) - (CLAUSILIIDAE)
- oshimae, Diplommatina oshimae H.A. Pilsbry, 1901 - (DIPLOMMATINIDAE)
- oshimae, Pupinella oshimae H.A. Pilsbry, 1901 - (PUPINIDAE)
- oshimae degenerata, Luchuphaedusa oshimae degenerata H.A. Pilsbry, 1905 - (CLAUSILIIDAE)
- oshimae tokunoshimana, Pupinella oshimae tokunoshimana H.A. Pilsbry & Y. Hirase, 1904 - (PUPINIDAE)
- oshimae yoroimana, Pupinella oshimae yoroimana H.A. Pilsbry & Y. Hirase, 1905 - (PUPINIDAE)
- oshimaensis, Trivirostra oshimaensis C.N. Cate, 1979 - (TRIVIIDAE)
- oshimai, Epimenia oshimai K. Baba, 1940 - syn of: Epimenia ohshimai K. Baba, 1940 - (EPIMENIIDAE)
- oshimai, Nipponatys oshimai T. Habe & T. Kikuchi, 1960 - (HAMINOEIDAE)
- oshimai, Fronsella oshimai T. Habe, 1958 - syn of: Fronsella ohshimai T. Habe, 1958 - (MONTACUTIDAE)
- oshimai, Devonia oshimai T. Kawahara, 1941 - syn of: Anisodevonia ohshimai (T. Kawahara, 1942) - (MONTACUTIDAE)
- oshimai, Octopus oshimai (M. Sasaki, 1929) - (OCTOPODIDAE)
- oshimana, Aegista kiusiuensis oshimana H.A. Pilsbry & Y. Hirase, 1903 - (BRADYBAENIDAE)
- oshimana, Luchuena eucharista oshimana (H.A. Pilsbry, 1902) - (ENIDAE)
- oshimanum, Clypeomorus oshimanum H.A. Pilsbry - syn of: Clypeomorus subbrevicula (C.H. Oostingh, 1925) - (CERITHIIDAE)
- oshimanus, Platyrhaphe hirasei oshimanus J.T. Kuroda, 1928 - (CYCLOPHORIDAE)
- oshimensis, Lima oshimensis G.B. III Sowerby, 1914 - syn of: Ctenoides concentricus (G.B. III Sowerby, 1888) - (LIMIDAE)
- oshimensis, Ctenoides oshimensis G.B. III Sowerby, 1914 - syn of: Ctenoides concentricus (G.B. III Sowerby, 1888) - (LIMIDAE)
- oshiroi, Nesiohelix oshiroi T. Habe & M. Chinen, 1980 - (BRADYBAENIDAE)
- oshiroi nobaruensis, Nesiohelix oshiroi nobaruensis M. Azuma, 1987 - (BRADYBAENIDAE)
- Osilinus, syn of: Genus Phorcus A. Risso, 1826 (TROCHIDAE)
- osimakiheijii, Helicarion osimakiheijii J.T. Kuroda, 1953 - (HELICARIONIDAE)
- osinii, Monacha osinii A. Villa, 1841 - (HYGROMIIDAE)
- osiridis, Orphanopusia osiridis (A. Issel, 1869) - (COSTELLARIIDAE)
- osiridis, Mitra osiridis A. Issel, 1869 - syn of: Orphanopusia osiridis (A. Issel, 1869) - (MITRIDAE)
- osiris, Struthioptera osiris H.J. Finlay & J. Marwick, 1937 † - (APORRHAIDAE) (FOSSIL)
- oskari, Helicina oskari A.J. Wagner, 1911 - (HELICINIDAE)
- oskarssoni, Similipecten oskarssoni H.H. Dijkstra, A. Warén & Gudmundsson, 2009 - (PROPEAMUSSIIDAE)
- oslavanensis, Theodoxus oslavanensis Rzehak, 1893 † - syn of: Theodoxus cyrtocelis austriacus (Rzehak, 1893 †) - (NERITIDAE) (FOSSIL)
- osloense, Westonoceras osloense E. Strand, 1934 † - (WESTONOCERATIDAE) (FOSSIL)
- osloensis, Mytoconula osloensis (E.L. Yochelson, 1977 †) - (PROTOCONCHOIDIDAE) (FOSSIL)
- osmagnum, Herewardia osmagnum Peñas & Rolán, 2017 - (PYRAMIDELLIDAE)
- osmani, Nicomedites osmani F. Toula, 1896 † - (BEYRICHITIDAE) (FOSSIL)
- osmani, Volvarina osmani J. Espinosa, J.A. Ortea & L. Moro, 2008 - (MARGINELLIDAE)
- osmani, Volutilithes osmani Abbass, 1967 † - (VOLUTIDAE) (FOSSIL)
- osmanica, Bulgarica bulgariensis osmanica (C.A. Westerlund, 1884) - (CLAUSILIIDAE)
- osmanicus, Albanites osmanicus (Arthaber, 1911 †) - (MEEKOCERATIDAE) (FOSSIL)
- osmanicus, Pronorites osmanicus Arthaber, 1911 † - syn of: Albanites osmanicus (Arthaber, 1911 †) - (PRONORITIDAE) (FOSSIL)
- osmanicus, Zonites osmanicus F. Riedel, 1987 - (ZONITIDAE)
- osmayi, Dentimargo osmayi J. Espinosa & J.A. Ortea, 2014 - (MARGINELLIDAE)
- osmenti, Liguus fasciatus osmenti W.J. Clench, 1942 - (ORTHALICIDAE)
- osmingtonensis, Anahoplites osmingtonensis (Owen 1971 †) - (HOPLITIDAE) (FOSSIL)
- osmondi, Amplirhagada osmondi G.A. Solem, 1988 - (CAMAENIDAE)
- osmonti, Beyrichites osmonti Smith, 1914 † - syn of: Parafrechites dunni (Smith, 1914 †) - (BEYRICHITIDAE) (FOSSIL)
- osmonti, Neanites osmonti Smith, 1927 † - (CLIONITITIDAE) (FOSSIL)
- osmunda, Pitar osmunda (T. Iredale, 1936) - (VENERIDAE)
- osmundsbergense, Pleurorthoceras osmundsbergense Kröger, 2013 † - (GEISONOCERATIDAE) (FOSSIL)
- osmundsbergense, Transorthoceras osmundsbergense Kröger & al., 2011 † - (PROTEOCERATIDAE) (FOSSIL)
- osmundsbergensis, Ambonychiopsis osmundsbergensis Isberg, 1934 † - (AMBONYCHIIDAE) (FOSSIL)
- osoensis, Hikidea osoensis A. Kaim & al., 2014 † - (COLLONIIDAE) (FOSSIL)
- Osoinia, Genus Osoinia Stevanovic, 1978 (CARDIIDA (UNASSIGNED)) (FOSSIL)
- osolei, Zospeum frauenfeldii osolei R. Slapnik, 1994 - (ELLOBIIDAE)
- Osorattis, syn of: Genus Notodiaphana K.H.J. Thiele, 1917 (NOTODIAPHANIDAE)
- osoriensis, Napaeus osoriensis (T.V. Wollaston, 1878) - (ENIDAE)
- osoriensis, Lyrodiscus osoriensis (T.V. Wollaston, 1878) - (ZONITIDAE)
- osorioae, Subniso osorioae (B.K. Raines, 2003) - (EULIMIDAE)
- osorioae, Hemiliostraca osorioae (B.K. Raines, 2003) - syn of: Subniso osorioae (B.K. Raines, 2003) - (EULIMIDAE)
- Osperleioceras, Genus Osperleioceras Krimholtz & Tazikhin, 1957 (HILDOCERATIDAE) (FOSSIL)
- Osperlioceras, Genus Osperlioceras Krimholtz & Tazikhin, 1957 (HILDOCERATIDAE) (FOSSIL)
- Ospriasolen, Genus Ospriasolen Conrad, 1868 (CARDIIDA (UNASSIGNED)) (FOSSIL)
- Osrea, syn of: Genus Ostrea C. Linnaeus, 1758 (OSTREIDAE)
- osrhomboides, Turbonilla osrhomboides A. Peñas & E. Rolán, 2010 - (PYRAMIDELLIDAE)
- ossaea, Vitrea ossaea I. Pintér, 1983 - (PRISTILOMATIDAE)
- ossea, Mangelia ossea (F. Nordsieck, 1968) - (MANGELIIDAE)
- ossea, Mangelia ossea P.M. Pallary, 1920 - syn of: Mangelia indistincta (T.A. de M. Monterosato, 1875) - (MANGELIIDAE)
- ossea, Imbricaria ossea L.A. Reeve, 1844 - syn of: Pterygia punctata (W.J. Swainson, 1821) - (MITRIDAE)
- osseocola, Adipicola osseocola R.K. Dell, 1987 - (MYTILIDAE)
- osseosa, Atagema osseosa (E.F. Kelaart, 1859) - (DISCODORIDIDAE)
- osseosa, Doris osseosa E.F. Kelaart, 1859 - syn of: Atagema osseosa (E.F. Kelaart, 1859) - (DORIDIDAE)
- ossetica, Caucasica ossetica (A. Mousson, 1863) - (CLAUSILIIDAE)
- ossetica, Clausilia ossetica A. Schmidt, 1868 - syn of: Megaleuxina derasa (A. Mousson, 1863) - (CLAUSILIIDAE)
- ossetica, Caucasigena ossetica Tavasieva, 1982 - syn of: Kokotschashvilia caucasicola (W.A. Lindholm, 1913) - (HYGROMIIDAE)
- osseticus, Deroceras osseticus H.R. Simroth, 1901 - (AGRIOLIMACIDAE)
- osseum, Bullia osseum (K.T. Menke, 1829) - (NASSARIIDAE)
- osseus, Murex osseus L.A. Reeve, 1845 - syn of: Purpurellus pinniger (W.J. Broderip, 1833) - (MURICIDAE)
- Ossiana, syn of: Genus Laona A. Adams, 1865 (LAONIDAE)
- ossiani, Philine ossiani W. Kobelt, 1896 - syn of: Laona finmarchica (M. Sars, 1859) - (PHILINIDAE)
- ossiania, Neptunea ossiania H.B.S. Friele, 1879 - syn of: Beringius turtoni (W.I. Bean, 1834) - (BUCCINIDAE)
- Ossiania, syn of: Genus Philine P. Ascanius, 1772 (PHILINIDAE)
- ossiansarsi, Philine ossiansarsi H.B.S. Friele, 1877 - syn of: Laona finmarchica (M. Sars, 1859) - (PHILINIDAE)
- ossiansarsi, Skenea ossiansarsi A. Warén, 1991 - (SKENEIDAE)
- ossica, Helix ossica O. Böttger, 1885 - syn of: Campylaea trizona olympica (J.R. Roth, 1855) - (HELICIDAE)
- ossicus, Napaeopsis ossicus (O. Böttger, 1885) - (ENIDAE)
- ossicus discolor, Napaeopsis ossicus discolor (O. Böttger, 1885) - (ENIDAE)
- ossisocia, Kelliella ossisocia T.A. Okutani & Y. Fujiwara, 2013 - (KELLIELLIDAE)
- ossium, Epitonium ossium T. Nakayama, 2000 - (EPITONIIDAE)
- ossoriensis, Mirayoldia ossoriensis Pronina, 1973 † - (YOLDIIDAE) (FOSSIL)
- ossovinarum, Pontohydrobia ossovinarum (N.I. Andrusov, 1890 †) - (HYDROBIIDAE) (FOSSIL)
- ostarrichi, Guildfordia ostarrichi J.M. Pacaud, 2017 † - (TURBINIDAE) (FOSSIL)
- ostashovense, Microcerithium ostashovense A.V. Guzhov, 2004 † - (CRYPTAULACIDAE) (FOSSIL)
- ostauri, Cypraecassis ostauri G. Humphrey, 1797 - syn of: Cypraecassis rufa (C. Linnaeus, 1758) - (CASSIDAE)
- ostauri, Zonitoides ostauri H.A. Pilsbry, 1926 - (GASTRODONTIDAE)
- ostbjorkae, Modiomorpha ostbjorkae Isberg, 1934 † - (MODIOMORPHIDAE) (FOSSIL)
- ostenfeldense, Latouchella ostenfeldense Skovsted, 2004 † - (COREOSPIRIDAE) (FOSSIL)
- ostenfeldi, Ranella ostenfeldi T. Iredale, 1937 - syn of: Ranella olearium (C. Linnaeus, 1758) - (RANELLIDAE)
- ostenfeldi, Alcithoe ostenfeldi T. Iredale, 1937 - syn of: Alcithoe larochei ostenfeldi (T. Iredale, 1937) - (VOLUTIDAE)
- ostenfeldi, Alcithoe larochei ostenfeldi (T. Iredale, 1937) - (VOLUTIDAE)
- ostensus, Larinopsis ostensus T. Iredale, 1936 - (VANIKORIDAE)
- ostenta, Doto ostenta R.F. Burn, 1958 - (DOTIDAE)
- ostenta, Marshallora ostenta E. Rolán & R. Fernández-Garcés, 2008 - (TRIPHORIDAE)
- ostentata, Doto ostentata R.F. Burn, 1958 - syn of: Doto ostenta R.F. Burn, 1958 - (DOTIDAE)
- ostentata, Yochelcionella ostentata Runnegar & Jell, 1976 † - (YOCHELCIONELLIDAE) (FOSSIL)
- ostentatus, Modiolus ostentatus T. Iredale, 1939 - syn of: Jolya rhomboidea (L.A. Reeve, 1857) - (MYTILIDAE)
- ostentus, Modiolus ostentus T. Iredale, 1939 - syn of: Jolya rhomboidea (L.A. Reeve, 1857) - (MYTILIDAE)
- Osteochiton, syn of: Genus Mopalia J.E. Gray, 1847 (MOPALIIDAE)
- Osteodesma, syn of: Genus Lyonsia W.H. Turton, 1822 (LYONSIIDAE)
- Osteodesma, syn of: Genus Thracia W.E. Leach in H.M.D. De Blainville, 1824 (THRACIIDAE)
- Osteomya, Genus Osteomya Moesch, 1874 (PHOLADOMYIDAE) (FOSSIL)
- Osteopelta, Genus Osteopelta B.A. Marshall, 1987 (OSTEOPELTIDAE)
- OSTEOPELTIDAE Marshall, 1987 - Family (GASTROPODA-VETIGASTROPODA [Subclass]-LEPETELLOIDEA [Superfamily])
- osteophila, Cocculinella osteophila B.A. Marshall, 1983 - (COCCULINELLIDAE)
- osteophila, Sagamilepeta osteophila (B.A. Marshall, 1983) - (LEPETIDAE)
- osteophila, Xylodiscula osteophila B.A. Marshall, 1994 - (XYLODISCULIDAE)
- osteovora, Rubyspira osteovora S.B. Johnson, A. Warén, Y.C. Lee & al., 2010 - (ABYSSOCHRYSIDAE)
- ostergaardi, Naria ostergaardi (W.H. Dall, 1921) - (CYPRAEIDAE)
- ostergaardi, Erosaria ostergaardi (W.H. Dall, 1921) - syn of: Naria ostergaardi (W.H. Dall, 1921) - (CYPRAEIDAE)
- ostergaardi, Mitra ostergaardi H.A. Pilsbry, 1920, 1921 - syn of: Nebularia fulvescens (W.J. Broderip, 1836) - (MITRIDAE)
- osterholzensis, Araeonema osterholzensis Heidelberger & Amler, 2002 † - (ARAEONEMATIDAE) (FOSSIL)
- osteri, Hydroginella osteri (F.P. Jousseaume, 1875) - (MARGINELLIDAE)
- osteri, Serrata osteri F.P. Jousseaume, 1875 - syn of: Hydroginella osteri (F.P. Jousseaume, 1875) - (MARGINELLIDAE)
- ostheimerae, Octomarginula ostheimerae R.T. Abbott, 1958 - syn of: Montfortia emarginata (H.M.D. de Blainville, 1825) - (FISSURELLIDAE)
- ostheimerae, Cuspivolva ostheimerae (C.N. Cate, 1973) - (OVULIDAE)
- ostiaria, Anodonta ostiaria H. Drouët, 1881 - syn of: Anodonta anatina (C. Linnaeus, 1758) - (UNIONIDAE)
- ostiarum, Anodonta ostiarum H. Drouët, 1881 - syn of: Anodonta anatina (C. Linnaeus, 1758) - (UNIONIDAE)
- ostiolum, Andrefrancia ostiolum (J.C.H. Crosse, 1870) - (ENDODONTIDAE)
- ostiolum, Micratys ostiolum M. Harzhauser, 2014 † - (HAMINOEIDAE) (FOSSIL)
- Ostioma, Subgenus Murchisonia (Ostioma) Tassell, 1980 (MURCHISONIIDAE) (FOSSIL)
- ostiorum, Assiminea ostiorum A.R.J.B. Bavay, 1920 - syn of: Assiminea grayana J. Fleming, 1828 - (ASSIMINEIDAE)
- ostium, Caveola ostium Garvie, 2013 † - (CANCELLARIIDAE) (FOSSIL)
- Ostlerina, syn of: Subgenus Platyceras (Platyostoma) Conrad, 1842 (PLATYCERATIDAE) (FOSSIL)
- Ostlingoceras, Genus Ostlingoceras Hyatt , 1900 (TURRILITIDAE) (FOSSIL)
- Ostodes, Genus Ostodes A. Gould, 1862 (NEOCYCLOTIDAE)
- Ostomya, Genus Ostomya Conrad, 1874 (LYONSIIDAE) (FOSSIL)
- Ostracarius, syn of: Genus Ostrea C. Linnaeus, 1758 (OSTREIDAE)
- ostracea, Tellina ostracea J.B.P.A. Lamarck, 1818 - (TELLINIDAE)
- ostracina, Placunopsis ostracina (von Schlotheim, 1820 †) - (ANOMIIDAE) (FOSSIL)
- Ostracites, syn of: Genus Ostrea C. Linnaeus, 1758 (OSTREIDAE)
- Ostracolethe, Genus Ostracolethe H.R. Simroth, 1901 (ARIOPHANTIDAE)
- Ostraea, syn of: Genus Ostrea C. Linnaeus, 1758 (OSTREIDAE)
- ostrarupis, Pseudoliva ostrarupis G.F. Harris, 1895 † - (PSEUDOLIVIDAE) (FOSSIL)
- ostrarupis pauper, Pseudoliva ostrarupis pauper G.F. Harris, 1895 † - syn of: Lisbonia pauper (G.F. Harris, 1895 †) - (PSEUDOLIVIDAE) (FOSSIL)
- ostraupis, Levarlatirus ostraupis (G.F. Harris, 1895 †) - (FASCIOLARIIDAE) (FOSSIL)
- ostraupis, Fusus ostraupis G.F. Harris, 1895 † - syn of: Levarlatirus ostraupis (G.F. Harris, 1895 †) - (FASCIOLARIIDAE) (FOSSIL)
- Ostrea, Genus Ostrea C. Linnaeus, 1758 (OSTREIDAE)
- ostreae, Myicola ostreae Hoshina & Sugiura, 1953 - syn of: Sinonovacula constricta (J.B.P.A. Lamarck, 1818) - (PHARIDAE)
- ostreaphila, Acanthochitona ostreaphila Sirenko & Saito, 2017 - (ACANTHOCHITONIDAE)
- ostrearum, Drillia ostrearum R.E.C. Stearns, 1872 - syn of: Pyrgospira ostrearum (R.E.C. Stearns, 1872) - (DRILLIIDAE)
- ostrearum, Calotrophon ostrearum (T.A. Conrad, 1846) - (MURICIDAE)
- ostrearum, Pyrgospira ostrearum (R.E.C. Stearns, 1872) - (PSEUDOMELATOMIDAE)
- ostrearum conradi, Calotrophon ostrearum conradi W.C. Mansfield, 1930 † - syn of: Calotrophon libertiense (W.C. Mansfield, 1930 †) - (MURICIDAE) (FOSSIL)
- ostreata, Psoronaias ostreata (P.M.A. Morelet, 1849) - (UNIONIDAE)
- Ostreavicula, Genus Ostreavicula Blanckenhorn, 1934 (BIVALVIA INCERTAE SEDIS) (FOSSIL)
- Ostrecolethe, syn of: Genus Myotesta W.E. Collinge, 1901 (ARIOPHANTIDAE)
- ostreicola, Parvanachis ostreicola (G.B. III Sowerby, 1882) - (COLUMBELLIDAE)
- ostreicola, Columbella ostreicola G.B. III Sowerby, 1882 - syn of: Parvanachis ostreicola (G.B. III Sowerby, 1882) - (COLUMBELLIDAE)
- ostreicola, Parvanachis obesa ostreicola (J.C. Melvill, 1881) - (COLUMBELLIDAE)
- OSTREIDAE Rafinesque, 1815 - Family (BIVALVIA-PTERIOMORPHIA [Subclass]-OSTREIDA [Order]-OSTREOIDEA [Superfamily])
- ostreiformis, Plicatula ostreiformis Stanton, 1896 † - (PLICATULIDAE) (FOSSIL)
- Ostreigenus, syn of: Genus Ostrea C. Linnaeus, 1758 (OSTREIDAE)
- Ostreinella, Genus Ostreinella Cossmann, 1914 (PTERIOIDEA (UNASSIGNED)) (FOSSIL)
- ostreion, Archiminolia ostreion C. Vilvens, 2009 - (SOLARIELLIDAE)
- Ostreites, syn of: Genus Ostrea C. Linnaeus, 1758 (OSTREIDAE)
- ostreivaga, Plicatula ostreivaga A. de Rochebrune, 1895 - syn of: Plicatula penicillata Carpenter, 1857 - (PLICATULIDAE)
- Ostreocamites, syn of: Genus Chama C. Linnaeus, 1758 (CHAMIDAE)
- ostreoides, Spondylus ostreoides Smith, 1885 - (SPONDYLIDAE)
- Ostreola, syn of: Genus Ostrea C. Linnaeus, 1758 (OSTREIDAE)
- Ostreola, syn of: Genus Ostrea C. Linnaeus, 1758 (OSTREIDAE)
- ostreola, Kondoa ostreola Unknown - (TROCHOMORPHIDAE)
- Ostreonella, Genus Ostreonella Romanowsky, 1890 (PTERIIDA (UNASSIGNED)) (FOSSIL)
- Ostreum, syn of: Genus Ostrea C. Linnaeus, 1758 (OSTREIDAE)
- ostricensis, Kutatissites ostricensis Stoykova, 1992 † - (ANCYLOCERATIDAE) (FOSSIL)
- ostrideslithos, Calliotropis ostrideslithos C. Vilvens, 2007 - (CALLIOTROPIDAE)
- ostrina, Fissurella ostrina L.A. Reeve, 1850 - syn of: Fissurella asperella G.B. I Sowerby, 1835 - (FISSURELLIDAE)
- ostrina, Nucella ostrina (A.A. Gould, 1852) - (MURICIDAE)
- ostrinus, Gradiconus ostrinus J.K. Tucker & M.J. Tenorio, 2011 - (CONIDAE)
- Ostroea, syn of: Genus Ostrea C. Linnaeus, 1758 (OSTREIDAE)
- ostroumovi, Parvicardium minimum ostroumovi B.M. Logvinenko & Y.I. Starobogatov, 1967 - (CARDIIDAE)
- ostroumovi, Euxinipyrgula ostroumovi (A.N. Golikov & Y.I. Starobogatov, 1966) - (HYDROBIIDAE)
- ostroumovi, Henslowiana ostroumovi Pirogov & Y.I. Starobogatov, 1974 - syn of: Pisidium henslowanum (R. Sheppard, 1825) - (SPHAERIIDAE)
- ostrovicensis, Montenegrina sturanyana ostrovicensis Z. Fehér & M. Szekeres, 2016 - (CLAUSILIIDAE)
- ostseensis, Pojetaia ostseensis Hinz-Schallreuter, 1995 † - (NUCULIDA (UNASSIGNED)) (FOSSIL)
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