Haplozyga armata (Nordstedt) Raciborski var. armata, Flora, Jena 81: 32, pl. 3-4, fig. 6. 1895.

Basionym: Gymnozyga armata Nordstedt, Acta Universitatis lundensis 3: 1, pl. 1, fig. 1-3. 1889.

(Fig. 15)

Cells 2 times greater in length than width, 27-42 × 14-21 μm, 6-10 μm broad at the apex and 14-15 μm broad at the isthmus. Semicells hexagonal; straight to slightly convex lateral margin; apex straight; 1 intumescence ornamented with a ring of robust spines and a small divergent indentation at the base; moderate median constriction; open to acute median sinus; smooth cell wall.

Material examined: BRAZIL, AMAPÁ, Macapá, Curralinho Lake, 02.VI.2007, C.B. Araújo (SP469217), 12.II.2008, C.B. Araújo (SP469224), 15.IV.2008, C.B. Araújo (SP469226), 13.V.2008, C.B. Araújo (SP469227), 15.VII.2008, C.B. Araújo (SP469228) .

Comments: Haplozyga (Nordstedt) Raciborski is a typically tropical genus and includes only two species and one taxonomical variety: Haplozyga armata var. armata (Nordstedt) Raciborski, Haplozyga armata var. raciborskii Förster and Haplozyga eckertii Förster. The species H. armata var. armata was originally described as Bambusina (Gymnozyga) armata Nordstedt by Nordstedt (1889). However, according to Bicudo & Menezes (2017), it was reclassified, in 1985, as Gymnozyga section: Haplozyga . Considering that specimens of Haplozyga are morphologically very distinct from those of Bambusina and of all other desmids genera, it worth maintaining it as a distinct genus until other polyphasic studies using molecular and phylogenetic analyses can confirm its taxonomic classification.

Distribution in Brazil: Goiás (Förster 1966); São Paulo (Förster 1966).