(Riedel and Sanfilippo, 1970, emend. 1978a)
The top of the zone is defined by the morphotypic last occurrence of Stichocorys peregrina and is coincident with the lower limit of the Pterocanium prismatium Zone.
Events included in the zone are:
- Didymocyrtis avita -> Didymocyrtis tetrathalamus
- Tm Phormostichoartus fistula
- Tm Phormostichoartus doliolum
- Spongaster pentas -> Spongaster tetras tetras
- Didymocyrtis penultima -> Didymocyrtis avita; Bm Theocorythium vetulum
- The lower limit of the zone is approximately synchronous with Bm Pterocanium prismatium; Tm Solenosphaera omnitubus omnitubus; Tm Solenosphaera omnitubus procera
The base of the zone is defined by the evolutionary transition from Spongaster berminghami to Spongaster pentas and is coincident with the upper limit of the Stichocorys peregrina Zone.
* In the tropical Indian Ocean, Johnson et al. (1989) used the upper limits of Phormostichoartus fistula and Phormostichoartus doliolum to divide this zone into three zones, Stichocorys peregrina (NR8), Phormostichoartus fistula (NR9) and Phormostichoartus doliolum (NR10).
Reference slides R 6.1, R 6.2 and R 6.3 from Sample 85-573-8-3, 69-71 cm.