1. Trans. Roy. Soo. Edinburgh, vol. xxxv (1888), pp. 419–428.
2. Geol. Mag., Vol. XII (1870), p. 69.
3. Morton G. H. : “Carboniferous Limestone of Anglesey,” pp. 52, 64.
4. Morton G. H. : “The Carboniferous Limestone and Cefn-y-Fedw Sandstone of the Country between Llanymynech and Minera,” 1879.