Suturothrix monoarmata, Singapore (21, 22), Thailand (23) and Brazil (24, 25) specimens from life (21, 22) and after protargol impregnation (23 – 25). 21, 22: A contracted slightly pressed specimen showing the distinct cortex (opposed arrowheads) and the single extrusome. 23: A malformed specimen. 24, 25: Dorsal views showing the right side suture (arrow) and monokinetids between dikinetids (arrowheads). Note triads in brush row 2. B, B1 – 3: dorsal brush rows; EX: extrusome; MA: macronucleus; MI: micronuclei. Bars 20 μm (Figs 21, 24, 25), 40 μm (23).