ABSTRACTThis monograph will appear in two parts. Part 1 includes notes on Llandovery stratigraphy and collecting localities, and on the preservation of the graptolites. Systematic descriptions are given of 14 genera and 51 species and subspecies (including 2 new and 3 un-named forms) belonging to the families Diplograptidae, Retiolitidae and Dimorphograptidae. Three species are recorded, with varying degrees of certainty, from this country for the first time. The Monograptidae will be described in Part 2.