In the northern Santa Rita Mountains, Pima County, Arizona, there are three named species of the helminthoglyptid landsnail Sonorella Pilsbry, 1900: Sonorella magdalenensis (Stearns, 1890), S. walkeri walkeri Pilsbry and Ferris, 1915, and S. rosemontensis Pilsbry, 1939. Of these taxa, Pilsbry (1939) originally named S. rosemontensis based on shell characters alone. Later, he dissected and described the reproductive organs from a specimen preserved in alcohol that was collected at a location different from the type locality. Subsequently, Walter B. Miller collected two snails, calling them S. rosemontensis, because they were collected at Pilsbry's S. rosemontensis locality. He noted that their male genitalia did not resemble those described by Pilsbry; rather, they closely resembled those of S. w. walkeri. Our examination of shell and reproductive anatomies of snails from the S. rosemontensis type locality near the north end of the Santa Rita Mountains, as well as specimens in the Santa Barbara Museum of Natural History collection lead us to conclude that snails previously referred to as S. rosemontensis are synonymous with S. w. walkeri, and that in his original description of the reproductive anatomy of S. rosemontensis, Pilsbry mistakenly dissected a specimen of S. magdalenensis.