Two new species of philometrid nematodes, Philometra gymnothoracis n. sp. and Philometroides marinus n. sp., are described from female specimens collected from the body cavity of the spotted moray, Gymnothorax moringa (Cuvier) (Muraenidae, Anguilliformes), and the cobia, Rachycentron canadum (Linnaeus) (Rachycentridae, Perciformes), respectively, from off the Atlantic coast of South Carolina. Philometra gymnothoracis n. sp. is mainly characterized by the conspicuously depressed mouth, the presence of 8 small cephalic papillae arranged in 4 submedian pairs, the esophagus with an anterior bulbous inflation, 2 small papilla-like caudal projections, the body length of the gravid female 435–760 mm, short ovaries, the length of larvae from the uterus 474–544 μm, and by the location in the host (body cavity). Philometroides marinus n. sp. differs from its congeners parasitizing marine and brackish water fishes mainly in having small cuticular bosses only on the anterior part of the body; in possessing 4 markedly large cephalic projections, each with 2 minute papillae, 2 large caudal projections, and in the location in the host (body cavity); the body length of subgravid and gravid females is 130–550 mm and that of larvae from the uterus 600–642 μm.