Eunotia formica Ehrenberg 1843, 1841: 414 . (Figs 30–36)

Valves slightly dorsiventral, almost linear with a gentle protuberance in the median region of the valve. Ventral margins are slightly concave. Dorsal margins are slightly convex. Inflated cuneate subcapitate apices. Valve length 24–72 μm, valve width 7–9 μm (measured at the center). Areolae slightly distinguishable in LM. Transapical striae almost parallel to radiate, evenly or unevenly spaced, 8–12 striae in 10 μm, slightly denser at the apices. Terminal nodules close to the apices, terminal raphe fissures long.

Material examined: — BRAZIL. Mato Grosso do Sul: Taguaruçú, Patos Lake, Upper Paraná River Floodplain, sediment, 23.III.2018, Ruwer et al. ( Nupélia UEM 18099–122); Batayporã, Garças lake, Upper Paraná River Floodplain, sediment, 19.IV.2017, Ruwer et al. ( Nupélia UEM 18068–69, 18071–72, 18074–76, 18084) .