Griffith & Brydone (1911); Brydone (1912) - Actinocamax plenus Zone
Biostratigraphical correlation: Equates with the greater part of the M. geslinianum Zone of current usage.
Lithostratigraphical correlation: Equates with the Plenus Marls Member, at the base of the Holywell Nodular Chalk Formation in southern England.
Age: Late Cenomanian