I consider Cerithiopsis iontha Bartsch, 1911 to be a nomen dubium based upon the following rationale. Bartsch (1911) relied upon three syntypes to describe C. iontha. Bartsch’s description includes a figure of one of the three. One of the three was deposited in the United States National Museum (USNM) and two were deposited in the Bermuda Museum and later transferred to the USNM. Unfortunately, the first one was lost and the remaining two could not be found among the material transferred to the USNM (Rolán & Espinosa, 1995). The figure presented by Bartsch is not consistent with his description in that he describes the protoconch as “whorls 2, well rounded, smooth,” but the figure shows a distinct peripheral cord or angle on the second protoconch whorl. The absence of the type material and the conflict between Bartsch’s description and his figure create sufficient ambiguity to consider C. iontha as nomen dubium. No other material has been located in the course of the author's studies over the past decades that match both Bartsch’s description and figure.

Rolán, E. & Espinosa, J., 1995. The family Cerithiopsidae (Mollusca: Gastropoda) in Cuba 3. The genus Cerithiopsis s. l., species with brown shell. Iberus, 13(2): 129-147.