Two new nematode species of Philometra Costa, 1845, P. carolinensis sp. n. and P. cynoscionis sp. n., are described from the spotted seatrout, Cynoscion nebulosus (Cuvier) (Sciaenidae, Perciformes) in estuaries on the Atlantic coast of South Carolina, USA. Philometra carolinensis (males and gravid and subgravid females) parasitic in the host's ovary is most similar to P. lateolabracis (Yamaguti, 1935) in female morphology, but distinctly differs from it in possessing conspicuously short spicules (81-87 µm long) with heavily sclerotized distal parts, the gubernaculum bearing a reflected dorsal barb, and in the length ratio of the gubernaculum and spicules (1:1.23-1.42) in the male. Philometra cynoscionis (only gravid females) found subcutaneously in the host's tissue (lateral to the ascending process of the premaxilla and also posteromedial to the length of each maxilla) is characterized mainly by the presence of cephalic papillae arranged in two circles (8 large papillae in outer circle and 6 small papillae in inner circle), the absence of caudal projections, the body size (length of gravid female 20-33 mm) and the location in the host.
Two new philometrid nematodes, Philometra overstreeti sp. n. and Philometroides paralichthydis sp. n., are described from female specimens collected from the southern flounder Paralichthys lethostigma Jordan et Gilbert (Paralichthyidae, Pleuronectiformes) in estuaries of South Carolina, USA. P. overstreeti is characterized by the presence of eight large, equal in size cephalic papillae, the absence of caudal projections, the body length of gravid females (14.10-27.06 mm) and the location in the host (among teeth). P. paralichthydis from the host's fins and the buccal cavity differs from its congeners mainly in possessing longitudinal cuticular ornamentations in addition to transverse ones or individual rounded bosses. It is the first species of Philometroides reported from flatfishes (Pleuronectiformes). A re-examination of type specimens of Margolisianum bulbosum Blaylock et Overstreet, 1999 showed that, in fact, nematodes belonging to two different species (now described to be new to science) and genera were confused in the original description of this taxon and in the diagnosis of Margolisianum. Since the male holotype of M. bulbosum cannot be identified to genus, Margolisianum bulbosum is a species inquirenda and a species incertae sedis. Consequently, Margolisianum becomes a genus inquirendus.