This Bulletin presents the taxonomy, temporal stratigraphy, palaeogeography, and ecology of the Middle Cambrian agnostid trilobites beginning with their arrival in the
Templetonian and reaching an acme of diversification in Undillan time; agnostids of the latest Middle Cambrian were described earlier (bpik, 1961b, 1967). The material described now contains numerous complete specimens which supplied information regarding the morphology and function of the agnostid skeletons so far not attainable with certainty from disjointed sclerites. The nine named and one unnamed (the initial Templetonian) zones are integrated into four geographically named stages, completing the scale of stages by starting with the Ordian and leading into the early Upper Cambrian the. continuous sequence of stages reads; Ordlan, Templetonian, Floran, Undillan, Boomerangian; followed by the early Upper Cambrian Mindyallan and Idamean. The scale of the zones of the agnostid species is the pivot of the biostratigraphic documentation; it is the time scale A. H. Westergaard introduced in 1946 in Sweden. I have implemented this scale in Australia in the field and in unpublished and published reports for over two decades, but 'on parole', in advance of the descriptions and illustrations of the relevant fossils which are presented here.
