Facts do not warrant the conclusion that there was a general transgression of the Coal Measure facies from north to south in Britain. The coal formation characterizing part of lower Carboniferous time in Scotland and Northumberland represents a separate episode quite unconnected with the later period of coal formation now represented by the Productive Coal Measures of the upper Carboniferous of those areas. The most striking feature in the distribution of British coals is the widespread occurrence of the important seams directly above and below the base of the Similis-Pulchra zone of the upper Carboniferous Ammanian. Although the early episodes of coal formation do not appear to have been related to a regular extensive transgression, there is no doubt that the time of cessation of coal formation became steadily later in the more southerly coal fields. This feature is no doubt linked with the progressively later onset of conditions leading to the formation of red beds.