A synopsis of the birds of North America - Audubon, John James, 1785 -1851 (Adam and Charles Black, 1839)

Synopsis of the classification of the animal kingdom - Nicholson, Henry Alleyne, 1844 -1899 (W. Blackwood, 1882)

Synopsis of the contents of Gesner's Museum of Natural History at Saint John, N.B. opened on the fifth day of April, 1842 - Gesner's Museum of Natural History. (s.n.], 1842)

Synopsis of the contents of the British Museum - British Museum (Printed by G. Woodfall, 1835)

Synopsis of the contents of the British Museum - British Museum (printed by G. Woodfall, 1839)

Synopsis of the contents of the British Museum - British Museum (printed by G. Woodfall, 1838)

Synopsis of the contents of the British Museum - British Museum (Printed by G. Woodfall, 1838)

Synopsis of the contents of the British Museum - British Museum (Printed by G. Woodfall and Son, Angel Court, Skinner Street, 1840)

Synopsis of the contents of the British Museum - British Museum (Printed by G. Woodfall, Angel Court, Skinner Street, 1840)

Synopsis of the contents of the British Museum - British Museum (Woodfall, 1842)

Synopsis of the contents of the British Museum - British Museum (printed by Woodfall, 1837)

Synopsis of the contents of the British Museum - British Museum (Printed by G. Woodfall, Angel Court, Skinner Street, 1836)

Synopsis of the contents of the British Museum - British Museum (printed by G. Woodfall, 1837)

Synopsis of the contents of the British Museum - British Museum (Woodfall, 1841)

A synoptical catalogue of British birds; intended to identify the species mentioned by different names in several catalogues already extant. Forming a book of reference to Observations on British ornithology - Forster, T. (Thomas), 1789 -1860 (Printed by and for Nichols, son, and Bentley, 1817)

Synoptical flora of North America - Gray, Asa, 1810 -1888 (Ivison, Blakeman, Taylor, and Co. [etc.,etc.], 1884)

Synoptical flora of North America: the Gamopetalæ, being a second edition of vol. I, part II, and vol. II, part I, collected - Gray, Asa, 1810 -1888 (Iverson, Blakeman, Taylor, and Company, 1886)

System der Ornithologie Westafrica's - Hartlaub, Gustav, 1814 -1900 (C. Schünemann, 1857)

System der Pterylographie. Nach seinen handschriftlich aufbewahrten Untersuchungen verfasst - Burmeister, Hermann, 1807 -1892 (E. Anton, 1840)

Systema avium - Wagler, Johann Georg, 1800 -1832 (sumtibus J.G. Cottae, 1827)

Systema avium Australasianarum = A systematic list of the birds of the Australasian region - American Ornithologists' Union. (British Ornithologists' Union, 1927)

Systema helminthum / auctore Carolo Mauritio Diesing ... Sumptibus Academiae caesareae scientiarum - Diesing, Karl Moritz, 1800 -1867 (W. Braumüller, 1851)

Systema naturæ in quo naturae regna tria, secundum classes, ordines, genera, species, systematice, proponuntur - Linné, Carl von, 1707 -1778 (Apud G. Kiesewetter, 1740)

Systema naturae, per regna tria naturae : secundum classes, ordines, genera, species cum characteribus, differentiis, synonymis, locis - Linné, Carl von, 1707 -1778 (Typis Ioannis Thomae, 1767)

Systema naturae per regna tria naturae : secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis - Linné, Carl von, 1707 -1778 (Typis Ioannis Thomae, 1767)

Systema naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis - Linné, Carl von, 1707 -1778 (Typis Ioannis Thomae von Trattner, 1767)

Systema natvræ per regna tria natvræ : secvndum classes, ordines, genera, species, cvm characteribus, differentiis, synonymis, locis - Gmelin, Johann Friedrich, 1748 -1804 (Typis Academicis, 1793)

Systema natvrae per regni tria natvrae secvndvm classes, ordines, genera, species, cvm characteribvs, differentiis, synonymis, locis - Linné, Carl von, 1707 -1778 (Io. Iac. Cvrt, 1760)

Systema venosum avium cum eo mammalium et inprimis hominis collatum : commentatio anatomica a gratioso medicorum ordine in literarum universitate Vratislaviensi D. III. M. Aug. A. MDCCCXLIV praemio ornata - Henry & Cohen, (Eduard Weber?, 1845)