Of this group, the species that was named first was Sorex vagrans Baird, 1858. Subsequently many other names were based on members of the group and these names were excellently organized by Jackson in his 1928 revision of the genus. Subsequent students of western mammals, nevertheless, have been puzzled by such problems as the relationship of (1) Sorex vagrans monticola to Sorex obscurus obscurus in the Rocky Mountains, (2) Sorex pacificus, S. yaquinae, and S. obscurus to one another on the Pacific Coast, and (3) S. o. obscurus to S. v. amoenus in California. Few studies have been made of these relationships. Clothier (1950) studied S. v. monticola and S. o. obscurus in western Montana and concluded that the two supposed kinds actually were not separable in that area. Durrant (1952:33) was able to separate the two kinds in Utah as was Hall (1946:119, 122) in Nevada. Other mammalogists who worked within the range of the vagrans-obscurus groups have avoided the problems in one way or another. Recently Rudd (1953) has examined the relationships of S. vagrans to S. ornatus.
MATERIALS METHODS AND ACKNOWLEDGMENTS
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´).