A taxonomic revision of three mid-Telychian monoclimacids

The important mid-Telychian biozonal index species Monoclimacis griestoniensis (Nicol, 1850) is redescribed and distinguished from two new species: Monoclimacis directa (formerly the ‘Monograptus cf. griestoniensis’ of Elles and Wood, 1911), and Monoclimacis woodae. Stratigraphically, directa appears a little before griestoniensis, whilst woodae is from the late griestoniensis to early crenulata Biozone.