Article: Uppermost Ordovician to Lower Silurian graptolite biostratigraphy of the Wye valley, central Wales

The graptolite biostratigraphy of the persculptus to magnus Biozone interval (upper Hirnantian to lower Aeronian) in the Wye valley near Rhayader, central Wales, is described. Possible refinements to the graptolite zonal scheme are indicated, including informal subdivisions of the acuminatus and acinaces Biozones. Quantitative faunal assessment indicates that diplograptid: monograptid ratios are useful in indicating stratigraphical level. Selected taxa are described, including three new species, Normalograptus? wyensis, Pseudoglyptograptus barriei and ' Orthograptus' cabanensis.