The material used for this study consists of numerous Heterocorallia from the V2bß, collected at Lives (near Namur, Belgium). The morphology and ontogeny of Heterophyllia ornata M'COY and Hexaphyllia mirabilis DUNCAN are described. The youngest stage observed shows 4 protosepta and 4 interseptal loculi in which the metasepta arise. This pattern of development differs from that usually accepted. The stratigraphie occurence of these species in Belgium is provided
