FIGURES 21–28 in Examination of type specimens for the genera Odontella and Zygoceros (Bacillariophyceae) with evidence for the new family Odontellaceae and a description of three new genera

FIGURES 21–28. Acigonium spinosa (Greville) P. A. Sims & D.M. Williams (Vema Cruise 17, core 107, 50cm). Fig. 21. Reproduction of plate 1, fig. 3 for Biddulphia spinosa from Greville (1859) (not to scale). Fig. 22. Valve with long hollow spines arising from marginal ridge, barely expanded mantle; scale bar = 10 μm. Fig. 23. Exterior flat with lanceolate valve face and central sternum extending between apical elevations; 6 spines arising from marginal ridge; scale bar = 20 μm. Fig. 24. Elevation with remains of ocellus on distal face and flattened summit; scale bar = 6 μm. Fig. 25. Valve centre with locular walls meeting at central annulus (sternum) (arrow); scale bar = 10 μm. Fig. 26. Valve tilted, marginal ridge with spines (which are the openings of rimoportulae) extending to base; scale bar = 20 μm. Fig. 27. Apical area, elevation with fractured ocellus on distal face, mantle with longitudinal and transverse costae; scale bar = 10 μm. Fig. 28. Flattened summit of elevation with ocellus on distal face; scale bar = 3 μm.