FIGURES 23–28 in Cymbella biseriata sp. nov.-a unique living species of Cymbella Agardh (Bacillariophyceae) with biseriate striae

FIGURES 23–28: Cymbella biseriata sp. nov. SEM from type material (MKNDC 012839). 23, 24. External views of whole valve. 25. External view of dorsal side of frustule. Transition between valve face and mantle is gradual and striae are biseriate and not interrupted on valve mantle. 26. Detail views of the mid-valve showing biseriate striae and external round openings of stigmata. 27, 28. Detail view of valve apices showing distal raphe ends and absence of APF. Scale bar = 10 μm (Figs 23–25), 5 μm (Figs 26, 28) and 2 μm (Fig. 27).