Plate 19
The 100 µm scale bar applies to all figures except the three enlargements (lb, 7b and 7c).
Fig. 1. Hexastylus dimensivus. Location of the smallest ornamentary knobs (fig. lb) is somewhat haphazard (in contrast to by-spines, which occupy nodal points and develop at right angles to the shell) Cp. with ornamentation of Diplosphaera hexagonalis (pl. 17). BSS 28B(IX/1309).
Figs. 2, 3, 5, 6. Hexastylus hexagonium, with varying numbers of spines. Note change in overall aspect (cp. figs. 3 and 6) due to differing contrast of photos. BSS 28B(IX/1194, IOW 134(F), BSS 28B(IX/1234) and BSS 21F EF Y32.
Figs. 4, 7. Hexastylus solonis. Fig. 7a: Before being broken, this specimen had six symmetrically arranged main spines. Note fine fibrils which are unified at the center as a symmetrical knot (with four fibrils in one plane and a fifth perpendicular to them; see fig. 7c). Fig. 7b: Detail of broken shell, with smooth surface layer (the epivitrium). Fig. 7c: Detail of the microsphere. Note also the layering, visible as a result of dissolution, in the broken fibril (lower left hand side). BSS 28B(IX/1195) and 28B(VII/1415). |
