Figure 8: Alternating arrangement of shell compartments in the three dimensions of space. Examples from Gulf of Aqaba, Red Sea; Recent.
A-B: Alternating chamber arrangement in the linear dimension (= biserial arrangement) as in Textularia foliacea Heron-Allen et Earland, SEM and X-ray graphs of lateral view. C-D: Alternating chamberlet arrangement in the planar (second) dimension, as in annular-concentric, discoidal shell of Planorbulinella elatensis Thomas, SEM graph of lateral view and equatorial section in transmitted light microscopy, coloured. E: Stereograph showing alternating chamberlets of a main chamberlet layer, with main stolon axes (horizontal arrows) and retrovert stolons feeding lateral chamberlet (vertical arrows). Schematic, not to scale. F-G: Alternating chamberlet arrangement in the third dimension producing a chessboard pattern, as in the spherical-concentric, globular shell of Sphaerogypsina globulus (Reuss), SEM graph of external view and centered section in transmitted light micrograph, coloured. H: Stereograph showing alternating chamberlets forming chessboard pattern. Schematic, not to scale.
Colours: red and blue: alternating generations of shell compartments; green: nepiontic, early stages including proloculus.
a; aperture; ch: chamber lumen; chl: chamberlet lumen; f: foramen; lchl: lateral chamberlet lumen.