The horse conch of the southeastern United States and eastern Mexico has been a subject of intermittent nomenclatural controversy: Fasciolaria papillosa G.B. Sowerby I, 1825 vs. Fasciolaria giganteaKiener, 1840. The original description of F. papillosa is very brief and is judged by some to be inadequate; no illustration or locality is provided, at least two described features are incompatible with the horse conch, and an extensive search has revealed no type material. Fasciolaria gigantea was introduced with a comprehensive description and figures that unmistakably depict the horse conch. The first figures associated with F. papillosa appeared more than two decades after its description (Reeve, 1847). Shells that Reeve figured as F. papillosa are conspecific with F. gigantea, which led to the subsequent controversy, but it is not clear that Reeve correctly identified F. papillosa. Fasciolaria gigantea has an extensive history of usage in modern literature, especially during the past 70+ years (300 vs. 3 reports of F. papillosa, 1953–2002; 18 of F. gigantea vs. 5 of F. papillosa, 2003–2017). Berschauer (2017) designated a shell figured by Reeve (1847) as neotype for Fasciolaria papillosa, which would make F. papillosa a senior subjective synonym of F. gigantea and disrupt prevailing usage, but that neotype designation does not meet specifications dictated by Articles 75.3 of the Code and therefore is invalid. We concur with authors who have recommended that Fasciolaria papillosaSowerby, 1825 be regarded as a nomen dubium. The name Fasciolaria giganteaKiener, 1840 should be used for the horse conch, now properly called Triplofusus giganteus (Kiener, 1840).