Two caryophyllaeid cestodes are described, Monobothrium fossae sp. n. from the blacktail redhorse Moxostoma poecilurum (Jordan) and Monobothrium mackiewiczi sp. n., from the Alabama hog sucker, Hypentelium etowanum (Jordan) from Alabama. M. ulmeri Calentine and Mackiewicz collected from the silver redhorse Moxostoma anisurum Robin and Raney in Lincoln County, Georgia constitutes a new locality record for the cestode, previously unknown south of Tennessee or east of Oklahoma. A table comparing the five North American species of Monobothrium is presented.