nomimoscolex guillermoi n. sp. and n. dechambrieri n. sp. are described from the gymnotiform fish gymnotus carapo from argentina. the new species are placed into nomimoscolex based on the cortical position of the vitelline follicles, and medullary position of the testes, ovary, and uterus. both species were compared to the 13 species considered valid in the genus. the combination of features distinguishing n. guillermoi from n. dechambrieri is (1) the position of the vagina to cirrus pouch (anterior or posterior vs always anterior respectively), (2) the total number of testes (41-85 vs 108-130 respectively), (3) the distribution of the vitelline follicles (arranged in dorso-lateral and ventro-lateral bands vs lateral bands respectively), (4) the length of the uteroduct (ending 58% vs 35% from posterior margin of mature proglottis respectively), and (5) the presence of gland cells in the scolex (unicellular glands in the apical region and the external margin of suckers vs the presence of unicellular glands in the apex and other grouped in a cluster medially to the suckers respectively).