Seven specimens of cyclocoelids (6 specimens representing Haematotrephus selfi n. sp. and 1 specimen representing a second unidentified species of Haematotrephus) collected by the late Dr. J. Teague Self, former professor, Department of Zoology, University of Oklahoma, Norman, Oklahoma, U.S.A., from the body cavities of 3 lesser yellowlegs, Tringa flavipes, (2 birds collected from Roger Mills County, Oklahoma on 23 and 29 August 1963, and 1 collected from Manitoba, Canada on 3 June 1964) and deposited in the Manter Laboratory of Parasitology, University of Nebraska, Lincoln, Nebraska are described. Haematotrephus selfi n. sp. can be distinguished from all other species in the genus that lack an oral sucker except Haematotrephus limnodromi by having intertesticular uterine loops. It most closely resembles H. limnodromi but differs from it by having a smaller body, a smaller pharynx, smaller testes, a shorter cirrus sac, and somewhat smaller eggs. In addition, H. selfi n. sp. lacks a uterine seminal receptacle.