Gray published several catalogues of the museum collections which discussed animal groups and described new species. He improved the collections to make them amongst the best in the world.
During his life he wrote over 500 academic papers, mostly on new species.
Gray was also interested in postage stamps; on 1 May 1840, the day the Penny Black first went on sale, he bought some to keep, thus making him the world's first known stamp collector.
Works (partial list)
1825 : An outline of an attempt at the disposition of the Mammalia into tribes and families with a list of the genera apparently appertaining to each tribe. Annals of Philosophy (ns) 10 : 337-344.
1826 : Vertebrata: Mammalia. (Appendix B in part). p. 412-415 in King P.P. (ed) Narrative of a survey of the intertropical and western coasts of Australia. Performed between the years 1818 and 1822. With an appendix, containing various subjects relating to hydrography and natural history. London: J. Murray, vol. 2.
1827 : Synopsis of the species of the class Mammalia. p. 1-391 in Baron G. Cuvier The animal kingdom arranged in conformity with its organization, with additional descriptions by Edward Griffith and others. (16 vols: 1827-1835). London: George B. Whittaker, vol. 5.
1828 : Spicilegia Zoologica, or original figures and short systematic descriptions of new and unfigured animals. Pt 1. London: Treuttel, Würtz & Co.
1830 : A synopsis of the species of the class Reptilia. pp 1–110 in Griffith E. The animal kingdom arranged in conformity with its organisation by the Baron Cuvier. London: Whitaker and Treacher, vol. 9 : 481 + 110 p.