The only external measurements of the animals used were those recorded by the collectors on the labels attached to the skins. These measurements were total length, length of tail and length of hind foot. Measurements of the ear have not been used since they were not in all instances recorded by collectors and since measurements of dry ears proved to be unsatisfactory. Only measurements of fully adult specimens have been used. The term fully adult is applied only to those specimens in which the auditory bulla is shiny and translucent, the permanent P4 is fully erupted and worn, and the tail is fully striped and penicillate. No one of these characters alone was accepted as proof of adulthood but only the three in combination. The following measurements of the skull have been used in the tables: _Greatest length._--From the most anterior tip of the nasals to the most posterior projection of the auditory bullae. _Greatest breadth across bullae._--From the most lateral projection of the auditory bulla on one side to the corresponding position on the other bulla. _Breadth across maxillary arches._--Greatest breadth across arches in a plane perpendicular to the long axis of the skull. _Width of rostrum._--Width of the premaxillae and the nasals taken immediately anterior to the upper incisors (not greatest width of nasals which is attained farther anteriorly). _Length of nasals._--Maximum length of a nasal bone. _Least interorbital breadth._--Least width between the orbits immediately posterior to the lacrimal processes. _Basilar length._--From the anterior margin of the foramen magnum to the posterior border of the alveolus of one of the upper incisors. Capitalized color terms are from Ridgway, "Color Standards and Color Nomenclature," Washington, D. C., 1912. Color determinations were made by comparing a masked area of pure color on the side of the animal with a masked rectangle of named color on Ridgway's plates in natural light always from the same angle. Abbreviations used for specimens examined from the various collections are as follows: