Observations on Upper Silurian Graptolites

As a result of a recent controversy not itself directly palaeontological, the graptolite zones of the Ludlow have come in for much implied criticism (e.g. Jones, 1937, p. 280). Unless this criticism is faced, the well-known zonal work of E. M. R. Wood (1900) will sooner or later fall into disrepute, and a considerable volume of stratigraphical work on the Upper Silurian of North Wales will likewise share this fate.