The 100 Ám scale bar applies to figs. la, 2a and 3a;
figs. lb, 2b and 3b each have their own (10 Ám) scale bar.
Figs. 1-3. Hexastylus hexagonium, showing varying shell sizes and degrees of development. Note, in fig. lb (a cross-section of the I-beam bubble-frame), that the hexagonal frames are visible on inner face of the shell. Figs. 2b and 3b: detail of cortical shell, including base of a main spine. Compare the degree of development of the shell (single vs. one-and-a-half layer in fig. 2b and 3b resp.) and of the by-spines (knobs vs. spines). BSS 28B(IX/1229, 1244 and 1291).