Specimens of the deep-water macrourid Nezumia liolepis were caught during a survey of the effects of the oxygen minimum layer on the vertical distribution of crustaceans, polychaetes, and fishes in the Gulf of California. Two specimens were each carrying one parasitic copepod each, initially judged to be identical to Lophoura tetraloba in almost all respects. An additional specimen of N. liolepis carrying one copepod was collected in the San Pedro Channel between San Pedro and Santa Catalina Island (southern California), and another specimen of N. liolepis carrying another copepod, collected between Cabo Corrientes (Jalisco) and Manzanillo (Colima), Mexico, was found in the collection of the California Academy of Sciences. Detailed inspection revealed several important differences between L. tetraloba from the South China Sea and Tosa Bay (Japan), and the new material, which along with the different depth and distribution, support the hypothesis of a new sphyriid species, described here as L. brevicollum. Lophoura tetraloba and L. brevicollum can be separated by the length of the neck, the number of dorsal and ventral depressions of the genito-abdomen, the length of the egg sacs, and by the general shape of the posterior processes. Finally, a new record and a new host for L. unilobulata, as well as some comments on the systematic position of Driocephalus are given.