Sir James was born on 6 September 1901 at Cambridge where he attended the Perse School. He received his geological education at Chelsea Polytechnic and the Royal College of Science. In 1923 he was appointed demonstrator in geology at the Imperial College of Science and Technology, London University, where he stayed until 1928; for his last two years there he also served as Warden at the pioneer Imperial College hostel. While at Imperial College he studied the Shineton Shales of the Wrekin district of Shropshire under the guidance of W. W. Watts and in collaboration with his life-long friend O. M. B. Bulman, and was awarded a Ph.D. in 1925. This work in Shropshire provided the stimulus for his continuing contribution on the Cambrian system and its faunas, and on trilobites of all ages. During this period he also recorded his observations on Tertiary crabs from Zanzibar, a group he was to return to in later years. In 1928 he obtained one of the two posts offered by the Geological Survey, being appointed Geologist. He undertook field work in the Dorking district as a prelude to an intended posting to the Survey office at York, but the death of G. W. Lee, then palaeontologist in Edinburgh, determined that Stubblefield should remain at the headquarters of the Survey at Jermyn Street in London. Internal transfers of the palaeontological staff left no member available to determine the fossils then accumulating from the current survey of the Shrewsbury district, and Stubblefield was asked by the Director to undertake this task because of his knowledge of the Lower Palaeozoic faunas of Shropshire. This transfer became long-term and thus began his association with, and eventual leadership of, the Palaeontological Department of the Survey, and secured the continuation of his notable contributions to palaeontology. The Shrewsbury commitment led to visits to the area during which new faunal horizons were discovered in the local Cambrian and Ordovician, including the Nemagraptus gracilis fauna from the Breidden Hills; other finds included the then earliest British eurypterid subsequently described by L. Størmer as the type of a new genus under the name of Brachyopterus stubblefieldi.

Stubblefield suggested that proparian trilobites may have arisen by paedomorphosis. Examples of the role of paedomorphosis in the evolution of species and of particular organs are reviewed. The cryptogenetic renewal of trilobites after the Cambrian resulted in distinctive major taxa, but their relationships to each other and to older groups remain unsolved. Similarities between early developmental stages should be re-assessed as a possible guide to relationships. The early Upper Cambrian, type species of the proparian Schmalenseeia is re-described. It was small, possibly world-wide in distribution, the exoskeleton thin, the parts not articulated, apparently forming a more or less rigid shield. It may have been a paedomorphic, planktic species, but its origin and relationships are obscure.

Cyclopyge genatenta Stubblefield, 1927, is interpreted from new material, and established as the type species of a new cyclopygid genus, Prospectatrix. The morphology of Prospectatrix shows that the cyclopygids and nileids are closely related, and together with the Taihungshaniidae, these families are included in an expanded concept of the Cyclopygacea. The subfamily Ellipsotaphrinae Kobayashi and Hamada, 1971 is excluded from the Cyclopygidae. Pelagic habits arose on at least five separate evolutionary lines among Ordovician trilobites: Prospectatrix lies near the origin of one of these. Cremastoglottos Whittard was derived from a robergioid ancestor by forward migration of the eyes.

Abundant specimens from the middle or upper Tremadoc beds in the Napton Fields Borehole, Warwickshire, are referred to one variable species, Kiaerograptus? quasimodo sp.nov. Two-stiped forms typical of Kiaerograptus co-exist with ‘one-stiped’ forms in which the first stipe consists only of Th 11. Rare specimens with three primary thecae gave rise to forms with one, two? or three stipes.

The Ordovician trilobite fauna of the Great Paxton Borehole, Cambridgeshire, consists of twelve species including the seven new species; Segmentagnostus stubblefieldi, Trinucleus bicallis, Bergamia artemis, Protolloydolithus salax, Ogygiocaris macrops, Merlinia anxia and Bohemilla tridens. The fauna recalls that from the lower Llanvirn of the Shelve area, Shropshire, but the possibility of an upper Llanvirn age remains.

The brachiopod fauna of the Gorran Quartzites of south Cornwall is described; it comprises five orthid genera. Three taxa are described under open nomenclature, and one new species is assigned to a new genus (Schalidomorthis stubblefieldi). The fauna supports the Llandeilo age suggested by accompanying trilobites. There is no brachiopod evidence to indicate that the quartzite pebbles of the Triassic Budleigh Salterton Pebble Bed are derived directly from the Ordovician of Cornwall.

The trilobite family Lichidae is represented in the Middle Ordovician of Virginia by silicified remains of species of Hemiarges and Amphilichas. One new subspecies, Hemiarges turneri Chatterton & Ludvigsen rasettii, is described. Development stages of both genera are illustrated. The bulla of H. turneri rasettii appears in the meraspis, whereas it is present in the protaspis of a Devonian species. The late metaprotaspis of Amphilichas has a small fixigenal spine, a feature shared with protaspides of the family Odontopleuridae.

Successive early Upper Devonian deposits penetrated in the Willesden No. 1 Borehole, along with their associated fossils, bear testimony to changing environments attributed to movements of the shoreline. The inferences drawn from these, and from marine-influenced deposits and faunas of similar age encountered elsewhere in the concealed strata, reinforce and refine the concept of a discrete Frasnian marine transgression. The event was probably linked with a similar, mid-Frasnian, movement in northern France.

Marine fossils have been recovered from the Downtonian–Devonian sequences of nineteen boreholes in southern England, most of which include strata referable to the Frasnian or early Famennian. A revised, Frasnian, age is suggested for deposits encountered in the Brightling Borehole and part of the Bolney succession. Upper Devonian strata with marine faunas are recognized in the Ashwell, Little Chishill and Northbrook boreholes, and late Silurian or very early Devonian at Lakenheath.

Reidentification of the macrofossils from the lowest Dinantian limestones of Lilleshall, northeast of Telford, indicates that these beds are older than previously reported and that they can be correlated with the early Tournaisian Hastarian Stage. The conodonts recovered confirm this age and are characteristic of the Siphonodella–Polygnathus inornatus Assemblage Biozone. This reassessment affects the Dinantian palaeogeography of the Midlands of England and the early Tournaisian coast-line in the Lilleshall area can be redrawn further to the north than it has usually been placed.

The history of research into the Lower Carboniferous rocks of Kent since Dines' 1933 account of the stratigraphy of the coalfield is outlined. Details of the boreholes that have proved Lower Carboniferous are listed, including notes of the significant fossils that have been identified. The age of the Lower Carboniferous rocks is discussed. Two boreholes yielded faunas of Tournaisian age and i4 proved rocks of Holkerian age. No younger Dinantian strata are known from Kent.