Local variations in the distribution of Silurian conodonts : an example from the amorphognathoides interval of the Welsh Basin: Microfossils from recent and fossil shelf seas / editors: J.W. Neale and M.D. Brasier Chichester: Ellis Horwood, for the British Micropalaeontological Society, 1981 p10-17:ill,maps / R.J. Aldridge and J.E. MabillardBooks/Monographs