"Four New Pocket Gophers of the Genus Cratogeomys from Jalisco, Mexico" by Robert J. Russell is a scientific publication written in the early 1950s. This specialized work focuses on the taxonomy of pocket gophers found in the state of Jalisco, Mexico, detailing the identification and descriptions of new subspecies within the genus Cratogeomys. The objective is to enhance the understanding of species variation and distribution in this particular region. The book outlines the findings from Russell's study, where he identifies two species of gophers, Cratogeomys gymnurus and Cratogeomys zinseri, and introduces four new subspecies: Cratogeomys gymnurus tellus, Cratogeomys gymnurus atratus, Cratogeomys zinseri zodius, and Cratogeomys zinseri morulus. For each subspecies, the author provides detailed descriptions of physical characteristics, geographical ranges, and diagnostic criteria that differentiate them from existing species. Additionally, Russell discusses the ecological implications of the distribution patterns and the adaptations that have led to such subspeciation among gopher populations within a relatively small geographical area. (This is an automatically generated summary.)