The 100 Ám scale bar applies to figs. la and 2a;
the other figures have their own scale bar.
Figs. 1-3. Spongodrymus octostylus. Note, in fig. la, the increasing density of the arborescent network towards the periphery of the shell, in contrast to the uniform density in fig. 3a. Figs. lb and 3b: details of the (pseudo)cubic microsphere. Note the transition from cylindrical to 3-bladed main spines. BSS 28B(IX/1315 and 1316).