THE HIRNANTIAN GRAPTOLITES NORMALOGRAPTUS-PERSCULPTUS AND GLYPTOGRAPTUS-BOHEMICUS - STRATIGRAPHICAL CONSEQUENCES OF THEIR SYNONYM

It is demonstrated that 'Glyptograptus' bohemicus is a junior subjecti ve synonym of Normalograptus persculptus. The first appearance of N. p ersculptus appears to be diachronous, posing problems for Hirnantian b iozonation. In China, N. persculptus co-occurs with N. extraordinarius . We favour here an extension downwards of the existing persculptus Bi ozone, the base being defined by the incoming of N. persculptus, with the lower part of the biozone designated the extraordinarius Subzone.