Stubblefield was born in Cambridge in 1901. He was a pupil at the Perse School, and went on to Chelsea Polytechnic and the Royal College of Science for his geological education. Here he had the stimulating company of two other promising students. One was O.M.B. Bulman, who became his lifelong friend, and with whom he worked on the early Palaeozoic rocks of Shropshire, collecting fossils and mapping the distribution of the rocks. A second was W.F. Whittard, also a great student of Shropshire fossils, who went on to become Professor of Geology in Bristol University, and a pioneer in promoting the value of off-shore geological mapping.
Stubblefield joined the Geological Survey of Great Britain in 1928, after five years teaching geology at the Imperial College of Science and Technology. Because of his expertise as a palaeontologist, the then Director of the Survey gave Stubblefield work in this field: identifying specimens collected by officers mapping rocks in different areas. Stubblefield became in due course leader of the Palaeontological Department, and was much concerned in preparations for the opening of the Geological Museum in South Kensington in 1935. In 1953 he became Assistant Director of the Survey, and in 1960 Director.
As Director he remained devoted to palaeontology: his work was characterised by thoroughness, acute observation, and the introduction of novel ideas. As a research worker in 1926 he had described a series of growth stages of a trilobite (a fossil arthropod) that he had collected, and shown unequivocally how the new segments of the body grew forward from the rearmost, settling a hitherto controversial matter.
In 1929 he had observed, in the colonial group of fossils the graptolites, that there were two distinct types of individuals, not a single type. His 1936 essay on how trilobites were classified was a penetrating and challenging masterpiece, containing the idea that a new group might arise from the arrested development of an ancestor. This was one of the early applications of such ideas to the evolution of invertebrate animals, and has since been widely followed.
The distribution and migrations of trilobite faunas in Lower Palaeozoic rocks were the subject of a 1939 essay, a pointer to the studies of fossil faunas and their distribution in time and space which have followed, and helped to modify or support physical evidence for reconstructing the geography of past worlds.
In 1959, as President of the Geological Society of London, he gave an address on the evolution in trilobites. This work included a graph showing the great numbers of trilobites that had evolved in early Palaeozoic time, and their decline to extinction at the end of that era. Since then details of this curve, and its fluctuations, have been greatly elaborated by more precise data, but the basic shape remains.
Much of Stubblefield's other palaeontological work is contained in official reports and summaries of progress in the Survey's work. Especially significant was his recognition of new fossil-bearing horizons in the coal measures, which greatly aided the search for additional coal resources during and after the Second World War, and in the early stages of exploration for resources of gas and oil. His curation and rearrangement of the Survey's collections of fossils was accompanied by much annotation of specimens, and the recognition of type specimens used in early, first descriptions of new faunas.
In addition to such official work Stubblefield served his fellow palaeontologists in many unsung but necessary ways in which his authority and meticulous care were so valuable. For many years he served as editor, and subsequently, from 1966 to 1971, as President, of the Palaeontographical Society, an organisation which has provided monographs on British fossils for over a hundred years. Stubblefield put much time and effort into organising the British contribution to the first international treatise on trilobites, published in 1959. For many years prior to, and for 10 years after his retirement, Stubblefield compiled the Zoological Record section on trilobites, an invaluable index and comment on the world-wide literature.
Stubblefield's career was exemplary in its devotion to pure science, with ever an eye on its practical application in the search for mineral resources. His wise counsel and guidance on the preparation of work for publication, the necessity for accuracy and the need for caution in expressing opinions based on inadequate evidence, were salutary guidance for palaeontologists at home and abroad.
Despite all the calls on his time, he was always willing to help and advise a colleague, young or old, and was a devoted family man and a keen gardener.
In early 1964, as a new MP and secretary of the Labour Party Standing Conference on the Sciences, I went to see James Stubblefield, writes Tam Dalyell. He was an enthusiast and a man for the long term, as befitted one whose professional experience involved geological time.
An incoming Labour government, he enthused, should embark on a project to create a tunnel under the Channel. Apart from economic advantage, and personal convenience, the project would boost engineering and geological activity in Britain. The same year, he was appointed a member of the Anglo- French Commission of Surveillance on the Channel Tunnel. He rapidly became one of the champions of the project and perhaps more than anyone else bestowed the imprimatur of his professional expertise on the feasibility of the project.
Stubblefield impressed on me the need where possible to introduce geology as a subject in the school curriculum. He emphasised that many pupils who found maths and physics altogether too daunting would take to geology, which had the academic attraction of being tactile. "Boys and girls like to feel objects, and geology is as good an introduction to lure them in to an interest in science and scientific method as you can find," he told me.
Above all, I remember Stubblefield's enthusiasm for what was beginning to be an exciting era for the North Sea. He said: "They will soon find oil in commercial quantities and you'd better prepare for a proper government control of what is found!" As usual, he was right.
Cyril James Stubblefield, geologist: born Cambridge 6 September 1901; Demonstrator in Geology, Imperial College, London 1923-28; geologist, Geological Survey of Great Britain 1928-47, Chief Palaeontologist 1947- 53, Assistant Director 1953-60, Director 1960-66; FRS 1944; President, Geological Society of London 1958-60; Director, Geological Survey in Northern Ireland 1960-66; Kt 1965; married 1932 Muriel Yakchee (two sons); died London 23 October 1999.