Fig. 6 in Palaeobiology of orthothecide hyoliths from the Cambrian Manto Formation of Hebei Province, North China

Fig. 6. Opercula of cupithecid hyolith Cupitheca convexa sp. nov. preserved as internal or external moulds, which are prepared from natural casts, collected from the Manto Formation (Cambrian Stage 4/5) in the Zuojiawu section of Tangshan, China. A, B. Internal moulds of opercula, NIGPAS 166337 A) and NIGPAS 166342 (B); showing exteriors covered with concentric ribs, protoopercula (indicated by white arrows) and imprints of bilobate cardinal →