Deeper water faunas, for example the Ordovician trilobite cyclopygid biofacies, may have even wider distribution in global terms (Fortey and Cocks, 1986; Cocks and Fortey, 1990) and thus be of little significance in dis- criminating which continent was close to an- other.However, they are important in a different way because they allow recognition of the mar- gins of these ancient cratonic areas, to which they were confined.