AbstractNamurian cliff sections are described in detail. A minimum thickness of about 76 m is ascribed to Namurian A and 198 m and 104 m respectively to Namurian B and C. Faunal marker bands enable the Chokierian, Marsdenian and Yeadonian Stages to be recognised and the detailed structure to be worked out and this confirms the structural interpretation of Dixon. The succession is correlated and compared with adjacent areas in Pembrokeshire and South Wales. The Marsdenian includes a fauna of highly variableSanguinolites. S. ovalisHind is redescribed and a lectotype chosen.