Abstract

The transfer of Encyonopsis frequentiformis Metzeltin & Krammer to the genus Gomphonema Ehrenberg is proposed based on observations using light and scanning electron microscopy. The taxon is characterized by lanceolate heteropolar valves, with both apices strongly capitate, two apical pore fields, and elongated areolae slit-like and the internal stigma opens in a slit. Heteropolarity of the specimens measured and other shared similarities with the genus Gomphonema (APF, areolae, external and internal aperture of the isolated pore, pseudosepta at both apices) allows us to classify this species into the genus Gomphonema. Morphological, ecological and distribution data in South America are presented and discussed based on available literature for this Neotropical taxon.