At high magnification, Uronema nigricans stands out due to its distinct frontal plate and the slightly ribbed pellicle (s. fig. 1 c). A reliable identification feature is the structure of the oral apparatus, which is, however, difficult to observe because Uronema nigricans is motile and hard to position ventrally. Then, one can recognize three adoral membranelles arranged one below the other and a right-sided undulating membrane (s. fig. 2). Another important feature is the paired cilia in the anterior part of the body. The posterior cilia stand individually. Since all my specimens were unfortunately filled with food, I could hardly discern the internal structure. A lens-shaped micronucleus is attached to the round macronucleus (s. fig. 1 b). I could not clearly identify the contractile vacuole. The caudal cilium (s. fig. 1 a) is only half the body length, as described by Foissner, Berger & Kohmann (1994).