The Scottish National Antarctic Expedition (1902 – 04) made the first topographical survey and geological assessment of Laurie Island, one of the South Orkney Islands. The expedition's surgeon and geologist, J. H. H. Pirie, provided competent geological descriptions but these were largely overshadowed by his misidentification of an obscure plant fossil as a graptolite. Erroneous confirmation by eminent British palaeontologists led to Triassic rocks being regarded as Lower Palaeozoic for fifty years. The mistake arose from the familiarity of all concerned with the geology of the Scottish Southern Uplands: they were led astray by the preconception that, as in Scotland, deformed ‘greywacke–shale’ successions would contain Lower Palaeozoic fossils. Other, more successful aspects of the expedition's geological investigations are less well known. Fossils acquired in the Falkland Islands expanded that archipelago's poorly known Devonian brachiopod fauna, but arguably the most important palaeontological discovery lay unrecognized for ten years. A limestone block dredged from the bed of the Weddell Sea contained Early Cambrian archaeocyath fossils which, had they been promptly identified, would have been the first record of this important Antarctic palaeofauna. Instead, the Weddell Sea material complemented fossils recovered on the opposite, Ross Sea side of the Antarctic continent during Shackleton's British Antarctic Expedition (1907 – 09).