Nitzschia soratensis has been often confused with this taxon and smaller valves of these taxa may not be distinguishable. Nitzschia soratensis has rounded apices, and distinctly rounded fibulae. The areolae are not resolvable in N. soratensis.
Nitzschia innominata has more elongate valves, with rounded to subrostrate apices.
Nitzschia abbreviata is very similar in shape. The striae of N. abbreviata have occluded areolae (SEM). The striae are biseriate close to the raphe canal.
The valves of N. frustulum are wider (3-3.9 µm).
BioData Reference
Krammer and Lange-Bertalot 2/2 Pl 68 Fig 1-8