Born on Feb 3rd, 1790, the third son of Thomas Mantell, and Sarah Austin of Peckham. His father, who traced his descent from Walter Mantell in 1540, was a cordwainer living in St Mary’s Lane, now called Station Street, Lewes. He is still remembered as the builder of the first Wesleyan Chapel in the town. Gideon Mantell was educated at an Academy in Lewes founded by John Button, and afterwards at a school in Wiltshire, his uncle being the Baptist minister at Westbury and Swindon. He was apprenticed to James Moore, a surgeon in Lewes, and then proceeded to St Bartholomew’s Hospital, taking with him a collection of fossils from the chalk which had already attracted his attention and interest. He returned to Lewes as soon as he had qualified, and entered into partnership with his former master, James Moore, and lived in Castle Place; he became Medical Officer of several parishes in the neighbourhood of Lewes and was appointed Surgeon to the Royal Ordnance Hospital at Ringmer. Encouraged by James Parkinson, a surgeon living at Hoxton who had published in 1804 *Organic Remains of a Former World*, he began to study geology seriously, and in 1815 published at Lewes an octavo volume, *A Sketch of the Geological Structure of the South-Eastern Part of Sussex*. In 1822 *The Fossils of the South Downs* appeared, with 42 plates engraved by Mrs Mantell and with the King as patron. In 1825 he contributed a valuable paper to the Royal Society on the Iguanodon, and with this fossil his name is now inseparably connected. In November, 1825, he was elected FRS. His next book, also illustrated, is known as *The Fossils of Tilgate Forest*, though it was published under the title *Illustrations of the Geology of Sussex* in 1827. Mantell in the meantime continued his medical work, took an active part in securing a free pardon for Hannah Russell in the Burwash case, and published in 1827 *Observations on the Medical Evidence Necessary to Prove the Presence of Arsenic in the Human Body*. In 1831 he became acquainted with Benjamin Silliman (1779-1866), Professor at Yale University and founder in 1818 of the *American Journal of Science*; the acquaintance ripened into a lifelong friendship and was the means of the honorary LLD being conferred upon him by the University of Yale in 1834. In 1833 he published *The Geology of the South-East of England*, with a dedication to the King, and in the same year he moved to 20 Steyne, Brighton, partly to reduce the labour of an extensive country practice, and partly on account of his health, which had given cause for anxiety. The move proved unsatisfactory from a professional point of view, and Mantell had serious thoughts first of emigrating to America, and later of buying a practice in London. He published in 1837 *Thoughts on a Pebble*, dedicated to his younger son, Reginald Neville Mantell; the book became very popular as a gift book, and there was a seventh edition in 1846. In September, 1837, he bought a practice at Clapham Common and sold a Geological Museum which he had collected with much pains. It was bought by the British Museum for £4000. *The Wonders of Geology* appeared in 1838 and soon established itself as a popular favourite. The eighth edition was published in England twelve years after his death; an edition appeared in America in 1839, and Dr Burchard, of Bonn, translated it into German. He also wrote the sketch of the “Geology of Surrey” which was published in Brayley’s *Topographical History of Surrey* in 1840. The following year, 1841, found him busy as a Member of the Councils of the Linnean and of the Geological Societies, and as Secretary of the Geological Section of the Royal Society. He was also one of the promoters of the Clapham Athenæum, which was established in 1841. With all these distractions it is clear that he did not neglect his medical practice, for his friends and patients at Clapham Common presented him with a purse of one hundred guineas as a birthday gift on Feb 3rd, 1844. He moved from his house in the Crescent, Clapham Common, in the autumn of 1844, to 19 Chester Square, SW. In this year he published *The Medals of Creation, or First Lessons in Geology and in the Study of Organic Remains* (2 vols, 8vo, illustrated, London, 1844). *The Thoughts on Animalcules, or a Glimpse of the Invisible World revealed by the Microscope*, with 12 coloured plates and 7 woodcuts, was issued in 1846, and in the same year *A Day’s Ramble in and about the Ancient Town of Lewes*, a small octavo with a frontispiece and vignette. *The Geological Excursions round the Isle of Wight and along the Adjacent Coast of Dorsetshire: illustrative of the most Interesting Geological Phenomena and Organic Remains* appeared first in 1847. A second edition with a supplementary chapter was published in 1850, and a third edition under the superintendence of Rupert Jones, FRS, was issued posthumously in 1854. Mantell was granted a pension of £100 a year from the Civil List in 1852. He died at his house, 19 Chester Square, on Nov 11th, 1852, and was buried in Norwood Cemetery. The memorial tablet in St Mary’s Church, Lewes, gives the year of his death incorrectly as 1853. Mantell married in May, 1816 - by special licence, for she was under age - Mary Ann, daughter of George Edward Woodhouse, of Maida Hill, London, W. She was educated to become a sufficiently good artist to illustrate some of her husband’s books and papers. She outlived him, but there is no mention of her at the time of his death, though she appears to have been living at Cambridge. A half-length portrait of her from a painting is in the possession of W M Woodhouse, Esq. There were two sons and two daughters of the marriage. Walter, the elder son, was appointed in 1848 “Commissioner for the allotment and purchase of lands in the middle island of New Zealand”. He died without issue. Reginald, the second son, was a pupil of Isambard K Brunel. He was engaged in railway construction in England and the United States. He died of cholera, unmarried, at Allahabad in 1857; and was superintending the building of a bridge over the Jumna when the Mutiny broke out. The elder daughter married John Parker, publisher to the University of Cambridge; the younger daughter died unmarried. Mantell was one of the many members of the medical profession who have made for themselves imperishable names in various branches of science entirely alien to their practice. He was amongst the pioneers in the study of fossils at a time when such study was considered impious. Ill health and a marked tendency to hypochondriasis must have made him “gey ill to live with” and accounted for the unnecessary acrimony which marks some of his discussions. A careful post-mortem examination was made of his body. The results are described in the *Medico-Chirurgical Transactions* for 1854, xxxvii, 167-170, with plates iv, and v. His spinal column is preserved in the College Museum (No. 4808/i) as an example of extreme lateral curvature which is remarkable from the fact that it does not appear to have been very noticeable during life. There is also a plaster cast of the spine in the College Museum (Special Pathology Part xxviii) with the number 4808/2. A kitcat portrait of Mantell is in the possession of W M Woodhouse, Esq, also a half-length portrait dated 1837 by J Masquerier, engraved by Samuel Stepney. Further portraits are one in a LLD gown from an engraving by W T Davey, and a small wax medallion executed in 1841 for presentation to Professor Silliman; but this was not considered good enough for the purpose. A fine engraving by W T Davey from a drawing by Senties is in the College Collection.