Four stage names are erected within the southern part of the type area of the Llandovery Series, south-east of Llandovery, Carmarthenshire, Wales. They are Rhuddanian, to incorporate the existing Lower Llandovery; Idwian for the Middle Llandovery, and Fronian and Telychian for the Lower and Upper parts of the Upper Llandovery. Correlation with the sequence of graptolite zones is suggested.
The base of the Llandovery at Llandovery is poorly exposed and unfossiliferous, and detailed correlation with other areas may always remain uncertain. Thus the base of the Llandovery Series, and hence the base of the Silurian System, is defined in Lapworth's classic locality at Dobb's Linn, Moffat, Scotland, at the base of the zone of Glyptograptus persculptus.