It is a zoological book. The hooded skunk, Mephitis macroura Lichtenstein, can be distinguished from the only other species in the genus, Mephitis mephitis Schreber, by the larger tympanic bullae, in the white-backed color phase by having some black hairs mixed with the white hairs of the back, and in the black-backed phase by having the two white stripes widely separated and on the sides of the animal instead of narrowly separated and on the back of the animal. The starting point for taxonomic work with Mephitis is A. H. Howell's 'Revision of the skunks of the genus Chincha (N. Amer. Fauna, 20, 1901). ' Of the species Mephitis macroura, Howell (op. cit. ) recognized three subspecies: M. m. macroura, M. m. milleri, and M. m. vittata. The species M. macroura is restricted to the arid region made up mostly of the Mexican Plateau. Also, wherever the species occurs beyond this Plateau, as for example in Guatemala, at San Mateo del Mar in Oaxaca, in the vicinity of Piedras Negras in Veracruz, and in southern Arizona, aridity is marked.