Ohrknorpel und äusseres ohr der Säugetiere; eine vergleichend-anatomische Untersuchung - Boas, J. E. V. (Johan Erik Vesti), 1855 -1935 ([Nielsen & Lydiche (A. Simmelkiær)], 1912)

L'Oiseau et la Revue francaise d'ornithologie - Société ornithologique de France. (Société ornithologique de France, 1977)

Les oiseaux des phosphorites du Quercy - Gaillard, Claude, 1861 -1945 (A. Rey; [etc., etc.], 1908)

Okens Lehrbuch der Naturgeschichte - Oken, Lorenz, 1779 -1851 (Bei Carl Heinrich Reclam, 1816)

Om slägtet Sorex, med några nya arters beskrifning - Sundevall, Carl J., 1801 -1875 (Kungliga Vetenskapsakademien, 1842)

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)

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)

Onoranze a Ulisse Aldrovandi nel terzo centenario dalla sua morte celebrate in Bologna - Aldrovandi, Ulisse, 1522 -1605 (P. Galeati, 1908)

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, 1956)

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

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)

Ornithologisches Centralblatt (1882)

The ornithology of the Straits of Gibraltar - Irby, L. Howard (Leonard Howard Lloyd), 1836 -1905 (R.H. Porter, 1895)

The ornithology of the Straits of Gibraltar - Irby, L. Howard (Leonard Howard Lloyd), 1836 -1905 (R.H. Porter, 1875)

Osservazioni naturali intorno alle cavallette nocive della Campagna Romana / [da Luigi Metaxa e Sebastiano Rolle] - Rolle, Sebastiano, (Vincenzo Poggioli, 1825)

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)

Otters and otter-hunting - Duncombe-Jewell, Ludovick Charles Richard 1866 - (L. Upcott Gill, 1908)

Our country's animals and how to know them. A guide to the mammals, reptiles and amphibians of Great Britain - Gordon, W. J. (Simpkin, Marshall, Hamilton, Kent, 1904)

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)

Outlines of comparative anatomy and medical zoology - Allen, Harrison, 1841 -1897 (Lippincott, 1874)

Outlines of comparative anatomy and medical zoology - Allen, Harrison, 1841 -1897 (J.B. Lippincott & co, 1869)

Outlines of comparative anatomy intended principally for the use of students - Fyfe, Andrew, 1754 -1824 (Printed by J. Pillans & Sons for Adam Black ... [etc.], 1818)

Outlines of general zoology - Baird, Spencer Fullerton, 1823 -1887 (Rudolph Garrigue, 1851)

Outlines of vertebrate palæontology for students of zoology - Woodward, Arthur Smith, 1864 -1944 (University Press, 1898)

Outlines of zoology - Thomson, J. Arthur (John Arthur), 1861 -1933 (Young J. Pentland, 1895)

Outlines of zoology - Thomson, J. Arthur (John Arthur), 1861 -1933 (Appleton, 1916)

Outlines of zoology - Thomson, J. Arthur (John Arthur), 1861 -1933 (H. Frowde and Hodder & Stoughton, 1899)

Outlines of zoology - Thomson, J. Arthur (John Arthur), 1861 -1933 (D. Appleton & Co, 1895)

Outlines of zoology - Thomson, J. Arthur (John Arthur), 1861 -1933 (D. Appleton & Co, 1892)

Outlines of zoology - Thomson, J. Arthur (John Arthur), 1861 -1933 (Pentland, 1899)

Outlines of zoology - Thomson, J. Arthur (John Arthur), 1861 -1933 (Young J. Pentland, 1892)

Outlines of zoology - Thomson, J. Arthur (John Arthur), 1861 -1933 (Humphrey Milford, Oxford University Press, 1929)

Outlines of zoology - Thomson, J. Arthur (John Arthur), 1861 -1933 (D. Appleton, 1906)

Outlines of zoology - Thomson, J. Arthur (John Arthur), 1861 -1933 (D. Appleton, 1895)

P. Boddaert, med. doct. urbis Ulissingæ exconsiliarii ... Elenchus animalium, volumen I : sistens quadrupedia huc usque nota, eorumque varietates : ad ductum naturae, quantum fieri potuit disposita - Boddaert, Pieter, 1730 -1795 (Apud C.R. Hake, 1784)