A new species of stichaeid fish referable to the genus Lumpenopsis Soldatov is described based on two specimens from Southern California. The Saddled Prickleback, Lumpenopsis clitella n. sp., is remarkably similar in body form and coloration to the type species of the genus, Lumpenopsis pavlenkoi Soldatov, 1916, known from the northwestern Pacific. The two species differ in number of anal-fin spines (one in L. clitella vs two in L. pavlenkoi), cheek squamation (absent vs present), and in modest details of meristics and coloration. Among North American pricklebacks, the Saddled Prickleback is most similar to the Y-Prickleback, Allolumpenus hypochromus Hubbs and Schultz, 1932. The holotype and only specimen on which the descriptions of that genus and species were based, reportedly lacked vomerine and palatine teeth, a character used to distinguish Allolumpenus from Lumpenopsis. The holotype of A. hypochromus cannot be located, but examination of two more recently collected specimens indicates the presence of both vomerine and palatine teeth in the Y-Prickleback. Consequently, Allolumpenus Hubbs and Schultz is considered a junior synonym of Lumpenopsis Soldatov. We provide a diagnosis of Lumpenopsis and key to the four included species: L. pavlenkoi Soldatov and Lumpenopsis triocellata (Matsubara) from the northwestern Pacific, and Lumpenopsis hypochromis (Hubbs and Schultz) and L. clitella n. sp. from the northeastern Pacific. Lumpenopsis exhibits a North Pacific distribution similar to that of other stichaeids.