This paper is about collecting, travel and the geographies of science. At one level it examines the circumstances that led to Isaac Lea's description in Philadelphia of six freshwater mussel shells of the family Unionidae, originally collected by John Kirk during David Livingstone's Zambesi Expedition, 1858–64. At another level it is about how travel is necessary in the making of scientific knowledge. Following these shells from south-eastern Africa to Philadelphia via London elucidates the journeys necessary for Kirk and Lea's scientific work to progress and illustrates that the production of what was held to be malacological knowledge occurred through collaborative endeavours that required the travel of the specimens themselves. Intermediaries in London acted to link the expedition, Kirk's efforts and Lea's classification across three continents and to facilitate the novel description of six species of freshwater mussel. The paper demonstrates the role of travel in the making of mid-nineteenth-century natural history and in developing the relationships and credibility necessary to perform the research on which classifications undertaken elsewhere were based.