The 100 µm scale bar applies to figs. la and 3;
the other figs. have their own scale bar.
Figs. 1-5. Saturnalis circularis. Specimens in figs. 1, 2 and 5 were broken in order to reveal the microsphere; orientations of figs. Ib and 2 are approximately opposite. Note the extremely fine network in figs. lb and 2, which appears to be a displaced ultrastructure of the microsphere (see also fig. 5). Fig. 2. Basal view of the microsphere. Figs. 4, 5: Note the roughness of the outer shell wall, in contrast to the smooth inner face of the shell. All BSS; 28B(X) (2x); 31B(F) EF W30; 28B(VIII/1121) and 28B(II).