Approximately 3,465 museum study skins and skulls were studied. Most of these were assembled at the University of Kansas Museum of Natural History, but some were examined in other institutions.
Specimens were grouped by geographic origin, age, and sex. Studies of the role of age and sex in variation were made. Because it was discovered that secondary sexual variation was negligible, both males and females, if of like age and pelage, were used in comparisons designed to reveal geographic variation.
External measurements used were total length, length of tail, and length of hind foot. After studying a number of cranial dimensions I chose those listed below as the most useful in showing differences in size and proportions of the skull. Figures 1 and 2 show the points between which those measurements were taken.
_Condylobasal length._--From anteriormost projection of the premaxillae to posteriormost projection of the occipital condyles (a to a´).
_Maxillary tooth-row._--From posteriormost extension of M3 to anteriormost extension of first unicuspid (b to b´).
_Palatal length._--From anteriormost projection of premaxillae to posteriormost part of bony palate (c to c´).
_Cranial breadth._--Greatest lateral diameter of braincase (d to d´).
_Least interorbital breadth._--Distance between medialmost superior edges of orbital fossae, measured between points immediately above and behind posterior openings of infraorbital foramina (e to e´).
_Maxillary breadth._--Distance between lateral tips of maxillary processes (f to f´).
[Illustration: FIGS. 1 AND 2. Showing where certain cranial measurements were taken. × 3-1/2. (Based on _Sorex vagrans obscurus_, from Stonehouse Creek, 5-1/2 mi., W junction of Stonehouse Creek and Kelsall River, British Columbia, [Female], 28545 KU.)]
In descriptions of color, capitalized terms refer to those in Ridgway (1912). In addition the numerical and alphabetical designations of these terms are given since a knowledge of the arrangements of these designations enables one quickly to evaluate differences between stated colors. Color terms which are not capitalized do not refer to any precise standard of color nomenclature.
In the accounts of subspecies, descriptions, unless otherwise noted, are of first year animals as herein defined. Descriptions of color are based on fresh pelages.