Strata in northern Cornwall, southwest England, have been established for the past 50 years as upper Devonian and lower Carboniferous, but the nature of the boundary has never been clarified. Recent work on the faunas in the beds at Launceston and in the Tintagel region on the coast has shown a conformable sequence which is here described. In the dark gray phyllites overlying the Tredorn phyllites in the California quarry at Boscastle, a sparse fauna has been found in which there are trilobites referred to Cyrtosymbole (Macrobole) cf. drewerensis and C. (M.) cf. duodecimae. These species are always associated with the goniatite Gattendorfia and are considered restricted to the G. zone, the lowest zone of the Carboniferous. As the Tredorn phyllites are Devonian, and the overlying dark phyllites lowest Carboniferous, the boundary may well be the junction between the systems, but is probably a fault junction.