FIGURES 2–25 in Taxonomy and ecology of Achnanthidium (Bacillariophyta, Achnanthidiaceae) from southeastern Brazil with the description of six new species

FIGURES 2–25. LM and SEM images of Achnanthidium acutum sp. nov. from type material (SP-427898), Rio Grande reservoir, São Paulo state. Figure 17 corresponds to the holotype. 2–12. LM views of raphe valves. 13–20. LM views of rapheless valves. 21. SEM external view of raphe valves showing striation pattern, axial and central areas. 22. SEM external detail of the distal raphe end. 23. SEM external view of the rapheless valve showing striation pattern, axial and central areas. 24. SEM internal view of the raphe valve. 25. SEM internal view of the rapheless valve. LM scale bar = 10 μm. SEM scale bars indicated in each figure.