Figs. la-c each have their own scale bar;
the 100 µm scale bar directly under fig. 2 applies to figs. 2-5.
Figs. la-c. Spongosphaera entodictyon. Figs. lb and 1c: details of the arachnoidal network. Note coral-like ornamentation consisting of extremely small knobs on all sides of the bars. BSS 28B(VI/516).
Fig. 2, 4. Spongosphaera leptoplegma. BSS 28B(II) and BSS 15B(F) EF B28.
Fig. 3. Spongodrymus elaphococcus. IOW 188(F). See also Pl. 28 fig. 1.
Fig. 5. Medullary shell of Rhizosphaera arcadophorum (see also plate 28) for comparison with fig. 3. Note difference in structure and in bar thickness, especially in the central part.