"Geographic Variation in the Pocket Gopher, Cratogeomys castanops, in Coahuila, México" by Robert J. Russell and Rollin H. Baker is a scientific publication produced in 1955. This work explores the various subspecies of the plateau pocket gopher, specifically the geographic distribution and variation within the state of Coahuila, Mexico. The authors delve into the ecological factors that influence these subspecies, underlining the complexity of their habitat and the impact of geographic features on their populations. The book systematically describes eleven subspecies of Cratogeomys castanops identified in Coahuila, referencing previous revisions and presenting new findings based on extensive field research and specimen collection. The authors discuss how factors such as topography and soil composition contribute to the isolation and differentiation of these subspecies. They thoroughly analyze physiological traits, including cranial measurements and pelage coloration, while also recognizing the behavioral ecology of these pocket gophers. Overall, the publication provides significant insights into the biodiversity of the region and contributes to a broader understanding of species adaptation and variation in response to environmental pressures. (This is an automatically generated summary.)