In 1926, Cushman described Rotalia beccarii var. tepida from San Juan Harbor, Puerto Rico. His publication illustrates a strew slide with many individuals, and no holotype was designated. Consequently, over the years, researchers have assumed that no holotype exists. A search of the Cushman Collection, however, discovered a slide labeled as holotype and it is so recorded in the Cushman Catalog of 1929. Here, this specimen is re-described and designated as a lectotype. All nine of the other surviving syntypes from the original collection in San Juan Harbor, Puerto Rico, now become paralectotypes. Hopefully, the designation of formal types for Ammonia tepida (Cushman) will help stabilize the taxonomy of this important species. Our study shows that the lectotype is morphologically distinguishable from other Ammonia types and that the distribution of Ammonia tepida is restricted to tropical shallow-water environments.