The millipede genus Apterourus Loomis, 1966, the only genus of the family Apterouridae Loomis, 1966 (Diplopoda: Chordeumatida: Striarioidea), contains two species and is rarely collected. We add a third species from Mt. Palomar, San Diego County, California, USA, Apterourus palomar Shear, Richart and Marek, new species.