Figure 50: Feathered grooves. All specimens figured as SEM graphs.
A-B: Ammonia beccarii ( ), Adriatic Sea, Recent. Peripheral and oblique - umbilical views. Note the ridges on the apertural face that initiate the feathering when the next chamber is added during ontogeny. C-D: Neorotalia calcar (d' ), Keij Island, Indonesia. Recent. Ventral view of an entire specimen and detail of a ventral feathered groove covered by a folded outer lamella. Note the imperforate nature of the cover and the orifices of the canal system. Compare: enveloping canal systems in Fig. 44. E-G: Unfeathered grooves in Ammonia ikebei ( et ), Eastern Kalimantan, Borneo, Upper Miocene. Peripheral view of entire specimen and details in oblique-umbilical and in dorsal views. Note the hemicircular attachment of the septal flap and the undivided umbilical plug that correspond to unfeathered septal grooves.
af: apertural face; f: foramen; fea: feathered grooves; ol: (folded) outer lamella covering a septal groove that is converted to an interlocular space; or: canal orifice; pil: pile; s: septum; sgr; septal groove (unfeathered); spgr: spiral groove (unfeathered); upl: umbilical plug.