FIGURES 63–71. Chaetoceros brevis. Figs 63–64, 67–71: culture material, strain PMFB1. Figs 65–66: field material. Figs 63–65: LM. Figs 66, 68: SEM. Figs 67, 69–71: TEM. 63) A complete chain. 64) Middle part of a chain showing single plate-like chloroplasts and peanut-shaped apertures. 65) Terminal part of a chain with plastid-like material within the setae. 66) Resting spore still covered with the remains of the girdle bands from the parent cell. Primary valve ornamented with numerous thin filamentous spines. 67) Detail of the valve with externally flattened tube of the rimoportula. 68) Internal view of the terminal valve showing the slit-shaped rimoportula (arrow) and silica projections extending from the marginal ridge (arrowheads). 69) Intercalary valve face showing central annulus and radially arranged parallel costae. Note the darker area in the central part of the valve. 70) Part of a girdle with bands ornamented with transverse costae. Note the connecting band with marked undulation. 71) Detail of a seta. Scale bars: 63= 20 μm; 64–65=10 μm; 66, 68–69=5 μm; 67, 70–71=1 μm.