Harry G. Seeley, British palaeontologist and geologist, was the son of Richard H. Seeley, a goldsmith, and his second wife, Mary Govier. He grew up in a family where scholarship and art were appreciated and developed an interest in geology at an early age. While apprenticed to his uncle, John Seeley, who was a conveyancing barrister, he became interested also in comparative osteology and prepared the skeletons of small animals, birds and fish. His friendship with S.P. Woodward, an assistant in the Department of Geology of the British Museum, made him aware of the extensive natural history collections of that institution. He published his first paper, "Description of two new species of Chalk starfishes" in the Annals of Natural History in 1858. Around 1859 he entered Sidney Sussex College, Cambridge, and although he did not obtain a qualification he was that year appointed assistant in the Woodwardian Museum of geology by Professor Adam Sedgwick. In this position he lectured, arranged the collection, catalogued fossils and conducted field studies, thus gaining considerable expertise in palaeontology. Despite suffering a mental breakdown in the mid-1860's his studies of fossils from the Cambridge Greensand led to the publication of many papers, as well as his Index to the fossil remains of Aves, Ornithosauria and Reptilia from the Secondary System of strata arranged in the Woodwardian Museum of the University of Cambridge (1869). In this publication he named nine new genera and 85 new species. It was soon followed by his Ornithosauria (1870), a review of the museum's flying reptile fossils, which remained a standard book of reference for a century.
In 1864 Seeley concluded that pterodactyls are not reptiles, but should be placed in a new sub-class allied to birds - a view that did not find favour with other palaeontologists. His work was profoundly anti-evolutionary and, in three papers between 1866 and 1882, he revived a widely dismissed theory pertaining to the vertebrate origins of the skull and limbs. Throughout his career he was a combative and controversial person.
In 1872 Seeley moved to London and married Eleonora J. Mitchell, with whom he had four daughters. Declining an offer of a post at the British Museum, he concentrated on writing for the next few years, publishing, among others, The fresh-water fishes of Europe (1886), and a complete revision of Phillips's Manual of geology (1884). Meanwhile he had accepted an appointment as professor of geography and geology at Queen's College, London, in 1876 and that same year was appointed professor of geography and lecturer in geology at King's College. An appointment to lecture for the Gilchrist Trust led him to visit most of the principal towns in England and Wales for this purpose. He had a wide interest in education and was a regular contributor to the Educational Times for many years. In 1885 he founded the London Geological Field Class, of which he remained the lecturer and leader for 21 years. In 1891 he published a most useful Handbook of the geology of London, primarily for these classes.
During the eighteen-eighties Seeley began his study of the fossil reptiles of the Karoo in the British Museum (Natural History), many of which had been presented by Andrew G. Bain* and his son Thomas Bain*. His descriptions of these fossils were published in a series of papers in the Philosophical Transactions of the Royal Society under the general title "Researches on the structure, organization and classification of the fossil reptilia" (Part 1, 1887 to Part VI, 1889; Part IV was read, but not published). He was particularly interested in the Anomodont reptiles (which include the genus Dicynodon) and their evolution into later reptiles and the earliest mammals. However, his studies were hampered by a lack of knowledge about the stratigraphy of the Karoo strata from which the fossils came, a shortcoming Seeley decided to rectify. In 1889 he obtained a grant from the Royal Society of London which enabled him, after visiting St Petersburg and Moscow for a look at their reptilian fossils, to visit the Cape Colony. His principal objects were to study the stratigraphy of the fossiliferous Karoo strata; to collect complete skeletons, rather than just skulls (as post-cranial remains were often ignored by fossil collectors at the time); and to study the fossils in South African museums and private collections. He was the first experienced palaeontologist to visit South Africa and his work generated much interest and support. After spending some time in Cape Town in July 1889 he left on a tour of the Karoo early in August, accompanied by Thomas Bain who acted as his guide. Long distances were travelled by train, but often also by horse and cart. They first went to Prince Albert and from there to Oudtshoorn and back; then on to farms with fossil sites in the Fraserburg Road (now Leeu Gamka) district and back again to Prince Albert on 20 August; to Beaufort West, Cradock and Kimberley, the northern limit of their travels; via De Aar to Colesberg, Ventersdorp and Burgersdorp, where they met Dr D.R. Kannemeyer*; to Aliwal North, where they visited Alfred Brown*; and via Molteno to Queenstown, where he received fossils from Dr William B. Berry* and where Bain took his leave. From there Seeley travelled with Dr W.G. Atherstone* by cart to Grahamstown, arriving on 8 September. On the tenth he delivered a public lecture there on "Scientific discoveries in South Africa". He then returned to Cape Town where he held a public lecture on the resources of the Cape Colony and on 16 September addressed the South African Philosophical Society on "Some scientific results of a mission to South Africa".
Seeley achieved much during his tour. He received many fossils from local collectors and also did some collecting himself. He identified the geological horizons from which fossils described earlier by Sir Richard Owen* had been collected; discovered an important Pareiasaurus skull and skeleton in the lower Karoo strata; and at Lady Frere, near Queenstown, the type specimen of Cynoghathus crateronothus was found and skulls of Gomphognathus (now Diademodon) collected. The specimens he sent to England from South Africa, and which were later presented to the British Museum (Natural History) by the Royal Society, kept him busy for years. They were described, among others, in a continuation of his "Researches on the structure, organization and classification of the fossil reptilia" (Part VII, 1892 to Part IX, 1894-1895). In Part VII he proposed five stratigraphical zones, based on their fossil content, namely the Mesosaurian, Pareiasaurian (now the Tapinocephalus zone of the Lower Beaufort Group), Dicynodont, Theriodont, and Zanclodont zones. These formed the basis for later more detailed stratigraphical studies. The final part of the series, published in six sections, constituted a complete review of South African fossil reptiles and represented a great contribution to the knowledge and classification of the fauna. Many more papers by him on South African fossil reptiles were published in the Geological Magazine, the Quarterly Journal of the Geological Society and the Annals and Magazine of Natural History between 1891 and 1908. His publications and specimens significantly advanced an understanding of the evolution of the Karoo reptiles. In recognition of his work he was elected an honorary member of the Geological Society of South Africa in 1896 and of the South African Philosophical Society in 1900. When the latter society became the Royal Society of South Africa in 1908 he was elected an honorary Fellow.
In 1891 Seeley was appointed lecturer in geology and mineralogy in the Royal Indian Engineering College at Coopers Hill, a post he held until the college was closed in 1906. In 1896 he became in addition professor of geology and minerality at King's College, London, until a few months before his death. A popular work by him, The story of the earth in past ages, was published in many editions between 1895 and 1920.
His scientific accomplishments were recognised by his election as a Fellow of the Royal Society of London (1879), the Geological Society of London, the Royal Geographical Society, the Linnaen Society, and the Zoological Society of London. He served on the council of the Geological Society, was its vice-president during 1900-1902, and received its Lyell Medal in 1885. Recognition outside Britain led to his election as a foreign member of the Philadelphia Academy (1878), the Imperial Geological Institute of Vienna (1880), the Imperial Society of Naturalists of Moscow (1889), and of the Senckenberg Natural History Society of Frankfurt (1895); and as a corresponding member of the Imperial Academy of Science, St Petersburg (1902).