John William Salter (1820–1869) was an English naturalist and geologist, best known for his work as palaeontologist to the Geological Survey of Great Britain. This is a complete catalogue of the Cambrian and Silurian fossils in the Geological Museum at the University of Cambridge. Preceded by a detailed introductory section on the Palæozoic system, the catalogue is arranged by geological strata, covering the various groups of Cambrian and Silurian fossils. The entries include detailed illustrations, along with references to the location of each fossil in the collection, its name and details of its place of origin. Revised by staff of the University and published posthumously in 1873, the catalogue also contains a substantial preface by Adam Sedgwick, famous for his role in the development of modern geology,which provides fascinating insights into the geological advances of the Victorian era.