Eunotia areniverma

The ventral margin is concave. The dorsal margin is broadly arched. The dorsal margin of smaller valves are more arched than the dorsal margin of larger valves. The apices are broadly rounded and usually unconstricted, though slightly constricted in the longer valves. The apices are set off by a change in slope of the dorsal margin. Helictoglossae are visible in the LM. One apical rimoportula is present at the center of the apex. Striae are mostly parallel and interrupted by a hyaline line at the ventral margin. Areolae are 28-30 in 10 µm.

Comparison of E. areniverma with E. monodon deserves further clarification. Siver et al. (2005, Plate 31: Figs 1- 4) illustrates specimens of E. monodon Ehrenberg which also possess broadly rounded ends. The dorsal margin becomes more sloped, with a more pronounced hump as frustules decrease in size. However, based on the original description, E. monodon has apices with more cuneate ends, such as the E. monodon illustrated in Patrick & Reimer (1966, Plate 11: Fig. 6) and Lange-Bertalot (1993, Taf. 22: Figs 6 -7). Eunotia monodon was described from North America and is found here along with E. monodontiforma Lange-Bertalot et Nörpel. When the name was adopted in Europe, it was used incorrectly to describe what should be E. major (W. Smith) Rabenhorst (see discussion in Lange-Bertalot 1993). This has created some confusion around the taxonomy of the E. monodon and the E. major groups. The ends of both E. major and E. monodontiforma are more set off from the rest of the valve relative to E. areniverma. The broadly rounded ends, less set off from the rest of the valve and the broadly arching dorsal margin are characteristic features of E. areniverma.