s. Measurements are in
millimeters.

The results of these studies were submitted to the Department of Zoology
and the Graduate School of the University of Kansas in partial
fulfillment of the requirements for the degree of Master of Arts (1952)
and are available in manuscript form at the Museum of Natural History
and the library of the University of Kansas.

EXPLANATION OF MEASUREMENTS

Caudal index.--the length of the tail expressed as a percentage of
the length of the head and body. The length of the head and body is
the collector's measurement of total length less the length of the
tail.

CRANIAL MEASUREMENTS OF LENGTH.

Condylobasilar length.--from the exoccipital condyle to the most
posterior point on the border of the alveolus of the upper incisor.

Alveolobasilar length.--from the posterior border of the alveolus
of the third upper molar to the posterior border of the alveolus of
the incisor.

Palatilar length.--from the anteriormost part of the posterior
border of the bony shelf of the palate to the posteriormost part of
the alveolus of the incisor.

Alveolar length of upper molar tooth-row.--from the most posterior
point of the alveolus of the third upper molar to the most anterior
point of the alveolus of the first upper molar.

MEASUREMENTS OF BREADTH.

Zygomatic breadth.--greatest transverse width.

Interorbital breadth.--the breadth of the interorbital
constriction.

Lambdoidal breadth.--between the lateralmost points of the
lambdoidal crest.

Prelambdoidal breadth.--between the medialmost margins of the
prominent fenestrae in the posterodorsal parts of the squamosal
bones. To these fenestrae Howell (1924:995) applied the adjective
"prelambdoidal," but other authors have used other names (see Hill,
1935:127).

Depth of braincase.--shortest distance from the ventral side of the
cranium at the suture between the basioccipital and basisphenoid
bones to the dorsal surface of the cranium (usually not
perpendicular to the long axis of the skull).

The history of our knowledge of _Microtus montanus_ in this area begins
with the early work of the United States Bureau of Biological Survey
directed by C. H. Merriam (1891), and participated in by Vernon Bailey
(1900, 1917), Merritt Cary (1911, 1917), and others. The changes in
nomenclature which grew ou