Eunotia eruca

Valves are weakly arcuate, with rounded ends. Both ventral and dorsal margins are distinctly sinuate, with undulations occurring 2 in 10 µm. Undulation of the central margin is bilateral, while more dorsal and ventral undulations toward the apices are alternate. Breadth in the center of valve is 8.7-11.6 µm at undulations (widest part), 6.3-8.0 µm between undulations (narrow parts), and 3.7-5.4 µm at the ends. Striae are interrupted by a sternum near the ventral margin. Areolae are visible in LM, numbering 21-27 in 10 µm. The raphe is short and curves onto the ventral mantle, near the apices.

While many authors continue to use the name Amphicampa eruca, Brightwell (1859) elevated A. eruca Ehrenberg 1954 from Ehrenburg’s subdivision of Eunotia, Amphicampa, to the genus level Eunotia eruca. Two years later A. eruca was superfluously synonymized with A. miriabilis Ehrenberg ex Ralfs in Pritchard 1861. Furthermore, Boyer (1927) lectotypified A. eruca for the genus Amphicampa, which was later re-lectotypified to A. mirabilis (Farr et al. 1979). Here we recognize the current valid name of this taxon as Eunotia eruca (Ehrenberg) Brightwell 1859, however there is not a consensus on recognition of the genus Amphicampa (as Amphicampa, Patrick and Reimer 1966, Kociolek 2000; as Eunotia, Krammer and Lange-Bertalot 1991; and awaiting detailed analysis, Round et al. 1990, Williams and Reid 2006). The few taxa recognized in the genus have a reduced raphe system and a sinuate ventral valve margin. Further work should be conducted to treat this species, as the classification in the Eunotiophycidae is in flux.