The 100 Ám scale bar applies to figs. 6a,b; other figures have their own bar.
Figs. 1-6. Acrosphaera spinosa. Figs. 1, 3-5: forma flammabunda. BSS 28B(VIII/922, 905, 875, 696). Note differences in spine length around larger pores. In fig. 6a, the focus is on the shell margin; in 6b, it is on the shell surface. See also plate 7, figs. 2-6, 8-11. Figs. 2, 6: forma nassiterna. BSS 28B(VIII/901) and 32B(F) EF B27.