Guide to Eunotia

Members of the Eunotiaceae (Eunotia, Actinella, Amphicampa) are unusual among the raphid diatoms in that frustules have a very short raphe system. The terminal nodules are positioned on the mantle. From the terminal nodule, the raphe slit lies on the valve mantle then slightly, or strongly, curves onto the valve face. As a result of this morphology, raphe branches visible in girdle view.

Valves of Eunotia are asymmetric to the apical axis. The dorsal margin is convex, smooth, or undulate. The ventral margin is straight or concave. Uniseriate striae extend across the valve face. Areolae of the striae generally lack hymenes and other occlusions. Usually one rimoportula present at an apex of each valve, although occasionally there may be two rimoportulae, or they may be absent.

Cells occur singly, free, or attached by mucilaginous stalks, or in long ribbon-like colonies. Species within Eunotia are widespread and diverse in acidic and dystrophic habitats.