Figure 9
The smooth and steady transformation of crystal morphology and size within a cone-shaped twinned crystal unit; starting with the nanofibrils within the POS (red arrows in (a)) and developing to the large plate/blade-shaped crystals at outer shell surfaces (b). (c) Intercalations of organic substance related to successive chamber formation cycles (undulating black lines) do not interrupt the steady transformation of crystal shape and size, nor the twinning characteristic of the calcite within the cone-shaped units. (a), (b), (c) BSE images of an etched sagittal cross-section through the entire shell wall of Pulleniatina obliquiloculata.
