GRAPTOLITE BIOSTRATIGRAPHY OF THE LOWER SILURIAN (LLANDOVERY AND WENLOCK) OF BOHEMIA

Nearly 50 sections through the Llandovery and Wenlock black shales of the Barrandian area (Bohemia) have been examined bed by bed. This has made possible the compilation of an improved and well defined graptoli te zonal scheme with much new biostratigraphic data included. A total of 268 graptolite species and subspecies have been found. Their strati graphic distribution allows the recognition of 27 graptolite zones: as census-acuminatus, vesiculosus, cyphus, triangulatus-pectinatus, simul ans, convolutus, sedgwickii, linnaei, turriculatus, crispus, griestoni ensis, tullbergi, spiralis, grandis, insectus, centrifugus, murchisoni , riccartonensis, dubius, belophorus, rigidus, ramosus-perneri, lundgr eni, parvus, nassa-frequens, praedeubeli-deubeli, ludensis, and severa l subzones. The biozones are defined by the vertical ranges of their ' index' species and are characterized by rich accompanying associations . The zonal scheme is correlated with graptolite sequences elsewhere.