On growth and form - Thompson, D'Arcy Wentworth, 1860 -1948 (University Press, 1945)

On the anatomy of vertebrates - Owen, Richard, 1804 -1892 (Longmans, Green, 1866)

On the anatomy of vertebrates ... - Owen, Richard, 1804 -1892 (Longmans, Green and Co, 1866)

On the archetype and homologies of the vertebrate skeleton - Owen, Richard, 1804 -1892 (John Van Voorst, 1848)

On the classification and geographical distribution of the Mammalia, being a lecture on Sir Robert Reade's foundation, delivered before the University of Cambridge ... May 10, 1859. To which is added an appendix "On the gorilla," and "On the extinction and transmutation of species." - Owen, Richard, 1804 -1892 (J. W. Parker and son, 1859)

On the domesticated animals of the British islands - Low, David. (Longman, Brown, Green & Longmans, 1845)

On the domesticated animals of the British islands : comprehending the natural and economical history of species and varieties; the description of the properties of external form; and observations on the principles and practice of breeding - Low, David, 1786 -1859 (Longman, Brown, Green & Longmans, 1845)

On the domesticated animals of the British islands: comprehending the natural and economical history of species and varieties; the description of the properties of external form; and observations on the principles and practice of breeding - Low, David, 1786 -1859 (Longman, Brown, Green, & Longmans, 1846)

On the form and structure of the Manatee (Manatus americanus) - Murie, James, 1832 -1925 (Zoological Society of London, 1872)

On the geology and natural history of the upper Missouri :Being the substance of a report made to Lieut. G.K. Warren, T.E. U.S.A - Hayden, F. V. (Ferdinand Vandeveer), 1829 -1887 (Printed by C. Sherman & son, 1862)

On the habits and instincts of animals - Swainson, William, 1789 -1855 (Printed for Longman, Orme, Brown, Green, & Longmans, 1840)

On the jaw musculature and relationships of Petrodromus tetradactylus (Mammalia, Macroscelidea) - Coldiron, Ronn W. (American Museum of Natural History, 1977)

On the minute structure and movements of voluntary muscle - King's College London. (Printed by R. and J. E. Taylor, 1840)

On the outskirts of empire in Asia - Zetland, Lawrence John Lumley Dundas, Marquis of, 1876 -1961 (W. Blackwood, 1904)

On the plains, and among the peaks, or, How Mrs. Maxwell made her natural history collection - Ridgway, Robert, 1850 -1929 (Claxton, Remsen & Haffelfinger, 1879)

On the power, wisdom and goodness of God, as manifested in the creation of animals, and in their history, habits and instincts - Kirby, William, 1759 -1850 (Carey, Lea & Blanchard, 1836)

On the reproduction and growth of the snow sheep (Ovis nivicola Esch) - Cherni͡avskiĭ, F. B. (Feliks Borisovich) (1962)

Onomasticon zoicon, plerorumque animalium differentias & nomina propria pluribus linguis exponens : cui accedunt Mantissa anatomica, et quaedam De variis fossilium generibus - Charleton, Walter, 1619 -1707 (Apud Jacobum Allestry ..., 1668)

Die Ontogenie der Primatenzähne : versuch einer Lösung der Gebissprobleme - Bolk, L. (Louis), 1866 -1930 (Verlag von Gustav Fischer, 1913)

Die Ontogenie der Primatenzähne - Bolk, L. (Louis), 1866 -1930 (G. Fischer, 1913)

Opinions and declarations rendered by the International Commission on Zoological Nomenclature - International Commission on Zoological Nomenclature (Printed by order of the International Trust for Zoological Nomenclature, 1947)

Opinions and declarations rendered by the International Commission on Zoological Nomenclature - International Commission on Zoological Nomenclature (Printed by order of the International Trust for Zoological Nomenclature, 1958)

Opinions and declarations rendered by the International Commission on Zoological Nomenclature - International Commission on Zoological Nomenclature (Printed by order of the International Trust for Zoological Nomenclature, 1955)

Opinions and declarations rendered by the International Commission on Zoological Nomenclature - International Commission on Zoological Nomenclature (Printed by order of the International Trust for Zoological Nomenclature, 1954)

Opuscula medica, quae reperiri potuere omnia, nunc primo simul edita - Drelincourt, Charles, 1633 -1697 (Apud Alberts & van der Kloot, 1727)

Opuscula subseciva, observationes miscellaneas de animalculis et plantis quibusdam marinis, eorumque ovariis et seminibus continentia - Baster, Job, 1711 -1775 (apud J. Bosch, 1762)

Orang-outang, sive homo sylvestris: or, The anatomy of a pygmie compared with that of a monkey, an ape, and a man. To which is added, A philological essay concerning the pygmies, the cynocephali, the satyrs, and sphinges of the ancients. Wherein it will appear that they are all either apes or monkeys, and not men, as formerly pretended - Tyson, Edward, 1650 -1708 (Printed for T. Bennett and D. Brown, and are to be had of Mr. Hunt, 1699)

The Orchid review (Orchid Review ltd.], 1909)

The orders of mammals - Gregory, William K. (William King), 1876 -1970 (The Trustees, 1910)

The Oregon naturalist (Naturalist Pub. Co, 1896)

Organic remains of a former world. An examination of the mineralized remains of the vegetables and animals of the antediluvian world; generally termed extraneous fossils - Parkinson, James, 1755 -1824 (Sherwood, Neely and Jones, etc, 1811)

The origin and relationship of the large mammals of North America - Grant, Madison. (Reprinted from the eighth annual report of the New York Zoological Society, 1904)

The origin and relationship of the large mammals of North America - New York Zoological Society. (1904)

Ornithologia methodice digesta, atque iconibus aeneis ad vivum illuminatis ornata - Lorenzi, Lorenzo. (In Aedibus Mouchianis, 1769)

Ornithologia methodice digesta, atque iconibus aeneis ad vivum illuminatis ornata - Lorenzi, Lorenzo. (In Aedibus Mouchianis, 1773)

Ornithologie Nordost-Afrika's : der Nilquellen- und Küsten Gebiete des Rothen Meeres und des nördlichen Somal-Landes - Heuglin, Theodor von, 1824 -1876 (T. Fischer, 1869)

Ornithologische Monatsschrift - Deutscher Verein zum Schutze der Vogelwelt. (Kommissions-Verlag der Creutschen Verlagsbuchhandlung, 1895)

Ornithologische Monatsschrift - Deutscher Verein zum Schutze der Vogelwelt. (Kommissions-Verlag der Creutschen Verlagsbuchhandlung, 1913)

Ornithologisches Centralblatt (L.A. Kittler, 1878)

Ornithologisches Centralblatt (L.A. Kittler, 1879)

The ornithologist's guide to the islands of Orkney and Shetland - Hullmandel, Charles Joseph, 1789 -1850 (Printed by Richard Taylor, Red Lion Court, Fleet Street, and published by the author, 31, George Street, Hull, 1837)

Ostéographie, ou, Description iconographique comparée du squelette et du système dentaire des Mammifères récents et fossiles : pour servir de base à la zoologie et à la géologie - Blainville, H.-M. Ducrotay de (Henri-Marie Ducrotay), 1777 -1850 (J.B. Baillière et fils, 1839)

Osteological assessment of Pleistocene Camelops hesternus (Camelidae, Camelinae, Camelini) from Alaska and Yukon - MacPhee, R. D. E. (American Museum of Natural History, 2016)

The Ottawa naturalist - Ottawa Field-Naturalists' Club (Ottawa Field-Naturalists' Club, 1893)

The Ottawa naturalist - Ottawa Field-Naturalists' Club (Ottawa Field-Naturalists' Club, 1892)

The Ottawa naturalist - Ottawa Field-Naturalists' Club (Ottawa Field-Naturalists' Club, 1895)

The Ottawa naturalist - Ottawa Field-Naturalists' Club (Ottawa Field-Naturalists' Club, 1896)

The Ottawa naturalist - Ottawa Field-Naturalists' Club (Ottawa Field-Naturalists' Club, 1907)

Our domestic animals in health and disease - Gamgee, John, 1831 -1894 (Maclachlan & Stewart, 1871)

Our domestic animals in health and disease - Gamgee, John, 1831 -1894 (Thomas C. Jack, 1861)

Our living resources : a report to the nation on the distribution, abundance, and health of U.S. plants, animals, and ecosystems - United States. National Biological Service. (U.S. Dept. of the Interior, National Biological Service, 1995)

Our living world; an artistic edition of the Rev. J. G. Wood's Natural history of animate creation - Wood, J. G. (John George), 1827 -1889 (S. Hess, 1885)

Our native birds; how to protect them and attract them to our homes - Lange, D. (Dietrich), 1863 -1940 (The Macmillan company, 1915)

Ouresiphoitēs Helveticus, sive, Itinera per Helvetiae Alpinas regiones facta annis MDCCII, MDCCIII, MDCCIV, MDCCV, MDCCVI, MDCCVII, MDCCIX, MDCCX, MDCCXI : plurimis tabulis aeneis illustrata - Scheuchzer, Johann Jakob, 1672 -1733 (Typis ac sumptibus Petri Vander Aa, 1723)

Outlines of clinical diagnostics of the internal diseases of domestic animals - Malkmus, Bernhard, 1859 -1925 (A. Eger, 1908)