[575]
[576]
[577]
The hooded skunk, Mephitis macroura Lichtenstein, can be distinguishedfrom the only other species in the genus, Mephitis mephitisSchreber, by the larger tympanic bullae, in the white-backedcolor phase by having some black hairs mixed with the white hairsof the back, and in the black-backed phase by having the two whitestripes widely separated and on the sides of the animal instead ofnarrowly separated and on the back of the animal. The startingpoint for taxonomic work with Mephitis is A. H. Howell's "Revisionof the skunks of the genus Chincha (N. Amer. Fauna, 20, 1901)."Of the species Mephitis macroura, Howell (op. cit.) recognized threesubspecies: M. m. macroura, M. m. milleri, and M. m. vittata.
The species M. macroura is restricted to the arid region made upmostly of the Mexican Plateau. Also, wherever the species occursbeyond this Plateau, as for example in Guatemala, at San Mateodel Mar in Oaxaca, in the vicinity of Piedras Negras in Veracruz,and in southern Arizona, aridity is marked. Whether the specieshas a continuous distribution from the southern end of the Mexicantableland southward to Dueñas in Guatemala is not known but itis unlikely that the lowland population at San Mateo del Mar onthe Pacific slope of Oaxaca has contact with M. m. macroura of theMexican Plateau and it is almost certain that the population, whichis here named M. m. eximius, from the arid coastal plain of easternMexico in Veracruz, has no connection with the upland population,M. m. macroura. The lowest elevation on the eastern slope of thePlateau from which we have record of the occurrence of this speciesis 4,500 feet at Jico. All along the eastern slope of the Plateau,between the elevations of approximately 2,000 and 4,500 feet, thebelt of lush, dense vegetation of the upper humid division of theTropical Life-zone constitutes a barrier to Mephitis and tends toexclude the hooded skunk from the arid territory below the humidbelt. Another kind of skunk, Conepatus tropicalis, lives in thehumid belt, at least on the eastern side of the Mexican tableland.How the population of Mephitis, which was sampled by us from[578]west and west-northwest of Piedras Negras, arrived there is unknownbut we think that its geographic range is not now connected withthat of the population on the Plateau. The same can be said of thelowland population at San Mateo del Mar in Oaxaca. There, on thePacific slope of the Mexican tableland, the lower humid division ofthe Tropical Lif