Gomphonema sp. 1

(Figs. 133-136)

Valves heteropolar, lanceolate, slightly linear. Apical ends cuneate, and basal ends attenuate-rounded. Axial are lanceolate, central area rectangular limited by a shortened striae. Raphe straight, with proximal ends, slightly dilated to pores. Striae short, parallel to slightly radiate toward the ends. Stigma absent. Length: 16.4 - 25 μm; width: 3.5 - 4.1 μm; striae 13 - 15 in 10 μm. The specimens observed are morphologically similar to G. rhombicum Fricke from Metzeltin et al. (2005), concerning valve shape and striae pattern. Besides that, G. rhombicum has a stigma and cuneate-rounded ends.

Material examined: BRAZIL, MATO GROSSO DO SUL: Batayporã, Garças Lake, 21.IX.2017, sediment, D.T. Ruwer (Nupélia UEM - 18068, 18072, 180086, 18090, 18093, 18095) .