Eunotia cf. bidens Ehrenberg,

Ber. K. Akad. Wiss. Berlin, 1841: 413. 1843.

(Figs. 69-71)

Valves with dorsal margin convex with two slightly prominent undulations, ventral margin slightly concave. Ends truncated, detached from the valve body. Striae parallel to radiate. Length: 33-76 μm; width: 10-13 μm; striae 10-14 in 10 μm. The population observed are consistent concerning some valve morphology features and dimensions with Eunotia bidens presented in Metzeltin & Lange-Bertalot (1998) and Metzeltin et al. (2005). However, the studied population was maintained as a conferatur due to variation in the morphology of the ends. E. bidens has subcapitate, obtusely rounded apices, and slightly detached.

Material examined: BRAZIL, MATO GROSSO DO SUL: Taquaruçú, Patos Lake, 23.III.2018, sediment, D.T. Ruwer (Nupélia UEM - 18098-122) .

Occurrence: first citation for Upper Paraná River floodplain.