In his preliminary revision of the genus Ceratopteris Benedict (1909) distinguished four species: C. thalictraides (L.) Brongn., C. pteridoides (Hook.) Hieron., C. deltoidea Benedict, and C. lockhartii (Hook. & Grev.) Kunze. Two more names were said to deserve further investigation: C. cornuta (Palisot) LePrieur and C. gaudichaudii Brongn. Since then the first four have not been in dispute, C. cornuta has become generally recognized, and C. gaudichaudii has remained doubtful (Fosberg, 1958). Most of the species of Ceratopteris are widely distributed. Ceratopteris thalictroides occurs in tropical Asia, Australia, and America (Benedict, 1909; Morton, 1967). Ceratopteris pteridoides is known from tropical America, subtropical South America, and continental tropical and subtropical eastern Asia (De Vol, 1957). Ceratopteris deltoidea is now known only from Florida, Central America, Jamaica, Porto Rico, Guyana, and Surinam. It has probably disappeared from Louisiana (Benedict, 1909; De Vol, 1956). Ceratopteris lockhartii is known from Trinidad, Guyana, and French Guiana (Benedict, 1909), C. cornuta from tropical and subtropical Africa, and C. gaudichaudii from Guam.