(Riedel and Sanfilippo, 1978a)
The top of the zone is defined by the morphotypic first appearance of Calocyletta costata and is coincident with the lower limit of the Calocycletta costata Zone.
Events included in the zone are:
- Bm Didymocyrtis mammifera
- Bm Calocycletta caepa
- Bm Dorcadospyris dentata
- Bm Liriospyris stauropora
- The lower limit is approximately synchronous with Tm Dorcadospyris ateuchus; Bm Siphostichartus corona
The base of the zone is defined by the morphotypic first appearance of Stichocorys wolffii and is coincident with the upper limit of the Stichocorys delmontensis Zone.
Reference slides R 22.1, R 22.2 and R 22.3 from Sample 85-573B-143, 61-63 cm.; R 23.1, R 23.2 and R 23.3 from Sample 85-573B-14-CC.