Summary The rocks of the Caradoc Series in the Cross Fell Inlier have been re-examined and their faunas, almost exclusively of shelly type, collected systematically. As a result a fairly detailed correlation with the stages of the south Shropshire succession is now possible. Bancroft’s published results are re-assessed and many of his conclusions, including that of the correlation between the shelly and graptolitic faunas, considerably modified. Detailed faunal lists and maps are appended, and correlations with other Ordovician sucessions, including parts of Scandinavia, discussed. It is proposed that in the Knock-Dufton district the term “ Corona Beds” should be confined to strata of Lower Longvillian age, and “Dufton Shales” used for beds ranging from Upper Longvillian to Pusgillian in age. The Caradoc strata near Melmerby are shown to be of Longvillian age and the name “Melmerby Beds” is proposed for them. The Pusgillian is equated, at least approximately, with the Zone of Pleurograptus linearis, and is believed to be older than the Diacalymene Beds, the lowest subdivision of the Ashgill Series. The Swindale or Staurocephalus Limestone of Swindale Beck is probably disconformable on the Dufton Shales there. The Ashgill Series near the head of Billy’s Beck is shown to be more fully developed than was thought, and the structural relations of the rocks there and nearby are discussed.