THE transient X-ray sources A1524—62 and A0535+26 were briefly observed by the University College, London, proportional counter spectrometer, experiment C on the Ariel V satellite (P. W. Sanford and J. C. Ives, unpublished). The resulting spectra help to complete the spectral history of these two sources, making seven sources for which there is now extensive spectral information. A general scheme emerges from these in which the sources with hard spectra (n ≲ 2) show little spectral evolution and those with soft spectra (n >2) exhibit marked softening with time. We discuss here this subdivision in relation to other properties of the sources.