This paper is an account of the megaspores borne by four species of Carboniferous Lycopod cones, referred to the genus Lepidostrobus. The megaspores (assigned to the genus Triletes) have been known isolated for more than twenty years, but the identities of their parent cone species have not previously been established. This study suggests the limits of variation that can reasonably be allowed in a ‘spore species’. Three of the cone species are emended in the light of their spore content, and a new species (Lepidostrobus allantonensis) is described. Using the megaspores as a diagnostic cone character, it has proved possible to correlate a species of isolated cone (Lepidostrobus dudius Binney) with the tree which bore it (Lepidodendron smile Kidst.). A cone previously attributed on doubtful evidence to Bothrodendron is shown to bear megaspores indistinguishable from those of a species reliably attributed to Lepidodendron, suggesting that the attribution to Bothrodendron is incorrect.