The name Didymaea alsinoides (Schltdl. & Cham.) Standl. has been incorrectly applied to a common and wideranging Mexican and Central American species whose correct identity is Didymaea Mexicana Hook. f. In this paper a lectotype is selected and designated for D. Mexicana. The characters separating these two frequently confused species are discussed. Further systematic studies of the genus Didymaea are suggested.
