Arguments are presented in favour of the continued use of the Beekmantown Group as the representative type of the Canadian Series, thus suppressing recognition of the formally correct Levis Formation of Quebec as the type-section of the Canadian. Thus defined, the Canadian/Champlainian boundary correlates with a level high in the Oepikodus evae Zone which corresponds to upper Didymograptus nitidus Zone. The lower Champlainian Whiterock Stage is redefined to embrace the stratigraphic interval of upper O. evae Zone to lower Pygodus serrus Zone; i.e., upper D. nitidus Zone to Didymograptus murchisoni Zone, inclusive. The Tableheadian Substage, after the Table Head Formation of western Newfoundland, is redefined as a substage for the upper part of the Whiterockian, with its base corresponding to the base of the "Amorphognathus" variabilis Zone which is within upper Didymograptus hirundo Zone. These biostratigraphically defined time-unit boundaries are with varying degrees of confidence correlated with rock-units established in eastern, western and southern North America.