Surirella brebissonii var. kuetzingii Krammer & Lange-Bertalot 1987 (LM: Figs 78–89, SEM: Figs 90–101, 106)

Observations:— LM: Valve outline ovate to elliptical with broadly rounded headpole and narrowly rounded footpole. Valve dimensions (n = 25): 14–25 μm long, 6.9–8.8 μm wide (measured at widest part of the valve), length/width ratio 1.4–1.6. Valve composed of two portions: central portion and outside portion (indicated in Fig. 83). Costa-stria bundles (CSBs) visible, alternated with over-fibula costae (OFCs) from pole to pole. CSBs reaching valve margins. CSBs parallel at valve middle part, radiate approaching apices. Fibulae well-developed, spanning c. 1/4 of valve width, not extending to midline, 6–8 in 10 μm.

SEM: Each CSB often composed of three costae and four striae (Figs 90–92). Striae multiseriate, composed of 3–5 rows of areolae, 23–25 in 10 μm (measured from SEM images, n = 4). Outside openings of areolae slit-like (Figs 92–95). Raphe canal located directly on mantle. Distal raphe endings simple and interrupting at both apices (Figs 93, 94, two arrows respectively). Internally, valve composed of two portions: central portion and outside portion (indicated in Fig. 97). Wall of raphe canal growing slightly into cell cavity leaving the portulae visible. Fibulae short, spanning c. 1/4 of valve width, not extending to valve midline (Figs 96–98). Raphe continuous at headpole (Fig. 99, wavy arrow), but interrupted at footpole (Fig. 100, two arrows). Three portulae produced between two adjacent fibulae (Figs 101, 106, three arrows). The areas between the fibulae form marginal trough-like depressions (Fig. 106).

Ecology and distribution:— Epilithic in freshwater river. Surirella brebissonii var. kuetzingi was found in the same sampling site with S. liubingii, for the environmental parameters, see above. It is commonly found in Europe with reports from Germany, France and Poland (Krammer & Lange-Bertalot 1987, Bey & Ector 2013, Szczepocka et al. 2018).