Figure 4: Embryonic and periembryonic chambers in Orbitoides spp. according to van Hinte's 1966 concept.
I: protoconch; II: deuteroconch; PAC: principal auxiliary chamber; PEC: principal epi-auxiliary chamber; AEC: accessory epi-auxiliary chamber. In our view, we prefer to call PAC an auxiliary and AEC an adauxiliary chamber.