Eunotia triodon may be distinguished from other large species of Eunotia with dorsal undulations by its moderatly arched valves and a consistent three broadly rounded undulations on the dorsal margin. Eunotia semicircularis may also have three undulations, but they are deeper undulations than E. triodon. Note that the degree of undulation (broad vs. deep) may be more relevant to identification than the number of undulations in distinguishing taxa.