We review the current usage of the species-group names Perognathus inornatus Merriam, 1889, for the San Joaquin Pocket Mouse and P. longimembris (Coues, 1875) for the Little Pocket Mouse. Wilfred Osgood, in two papers published 18 years apart at the beginning of the 20th Century, provided conflicting applications of these names, with his second assignments in common use since 1918. Contrary to this prevailing usage, we show that the skull of the holotype of longimembris is best allocated to the San Joaquin form, as Osgood had originally concluded in 1900. To maintain stability and universality of current usage (International Code of Zoological Nomenclature: Article 75.6), we propose a neotype from the Antelope Valley of California as a replacement for Coues's holotype of longimembris.