The names Polygnathodella Harlton and Cavusgnathus Harris and Hollingsworth and Idiognathoides Harris and Hollingsworth were proposed at nearly the same time, in papers referring to conodonts of about the same age from the same general region. Since then, conodont workers have considered Idiognathoides to be a junior synonym of Polygnathodella but it now proves to be a junior synonym of Cavusgnathus. Polygnathodella and Cavusgnathus are shown to form a transitional series.