Figure 46: Expanse chambers and calyces.
A: Sketch of ultimate and penultimate expanse chambers, not to scale. B: A cut-out portion of five successive expanse chambers, cut in an oblique direction with respect to the shell axis, schematic, not to scale. Lamellation of walls omitted. C: Ultimate and penultimate expanse chambers in Planogypsina squamiformis (Chapman). Gulf of Aqaba, Red Sea; Recent. SEM graph. D-G: Expanse chambers with calyces in Miniacina miniacea (Pallas), Gulf of Aqaba, Red Sea; Recent. D-F: SEM graphs, G: thin section in transmitted light. D: broken surface perpendicular to the axis of a branch of the arborescent shell: the expanse chambers are grouped around tubular extensions of the peristomes of earlier chambers. E: a fragment of shell showing the inner surfaces of two successive expanse chambers. Note the alternating arrangement of the calyces. F: radial spreading of ultimate expanse chamber at the foot of an arborescent shell, thus enlarging the shell's surface of attachment. G: centered section near and parallel to the surface of attachment, so cutting the latest, outermost expanse chambers at diminishing angles.
a: aperture; ax: shell axis; cy: calyx; p: pore; pr: proloculus; puch: penultimate expanse chamber; sut: suture of expanse chamber; tpa: tubular passage connecting parts of expanse chamber; uch: ultimate expanse chamber.