(Hays, 1970, emend. Foreman, 1975)
The top of the zone is defined by the evolutionary transition of Eucyrtidium calvertense to Eucyrtidium matuyamai and is coincident with the lower limit of the Eucyrtidium matuyamai Zone. The upper limit of this zone is similar to the upper boundary of the Phi Zone in Antarctic sediments (Hays, 1965). Kling (1973), in North Pacific sediments, used the morphotypic first appearance of Eucyrtidium matuyamai as the upper limit of this zone.
The base of the zone is defined by the morphotypic last appearance of Stichocorys peregrina and is coincident with the upper limit of the Sphaeropyle langii Zone.
Reference slides R 53.1, R 53.2 and R 53.3 from Sample 18-173-9-3, 24-30 cm.