(Maurrasse and Glass, 1976)

The top of the zone is defined by the evolutionary transition of the Lithocyclia aristotelis group to Lithocyclia angusta and is coincident with the lower limit of the Theocyrtis tuberosa Zone.

Events included in this zone are:

- Tm Dictyoprora armadillo

- Tm Lophocyrtis jacchia

- Tm Calocyclas turris; Tm Thyrsocyrtis bromia; Tm Thyrsocyrtis rhizodon; Tm Cryptocarpium azyx

- The lower limit of the zone is approximately synchronous with Tm Thyrsocyrtis lochites; Tm Calocyclas bandyca; Tm Calocyclas hispida; Tm Lychnocanoma bellum; Tm Podocyrtis papalis

The base of the zone is defined by the mophotypic last appearance of Thyrsocyrtis tetracantha and is coincident with the upper limit of the Calocyclas bandyca Zone.

Reference slides R 36.1, R 36.2 and R 36.3 from Sample 41-366-10-5,
53-60 cm.