UU--Museum of Zoology, University of Utah.
WC--Collection of Edward R. Warren, Colorado College.

Of the external measurements, only the total length and
the length of the tail are recorded in table 1. Some field
collectors measured the ear from the notch and others from
the crown; most collectors measured the length of the hind
foot to the nearest millimeter rather than in tenths of a
millimeter, as would have been desired. Consequently, I
decided against using the lengths of the ear and hind foot in
the study here reported on.

The measurements of the skull were made as shown in figure 1.

[Illustration: FIG. 1. Dorsal view of skull and a lateral and
a medial view of the right lower jaw to show points between
which measurements of the skull were taken. x 1-3/4. Based on
_Eutamias ruficaudus ruficaudus_, from 6 mi. S St. Mary, 6500
ft., Glacier Co., Montana. A to A'--greatest length of skull;
B to B'--length of nasals; C to C'--zygomatic breadth; D to
D'--least interorbital constriction; E to E'--cranial
breadth; F to F'--inner mandibular length; G to
G'--condylo-alveolar length of mandible.]

A total number of 434 specimens are listed as examined in
this study, and additionally, numerous other specimens were
superficially examined in the United States Biological
Surveys Collection. Bacula of each of the named kinds of
chipmunks in this paper, were examined.

Whenever two or more samples are stated to be significantly
different, the meaning is that the difference is
statistically significant.

The geographic distribution of each subspecies and the
localities of specimens or series of specimens are plotted on
the map (fig. 2).

When comparisons were made to ascertain specific and
subspecific differences, only adults, or animals in which the
enamel was worn through on the permanent P4 and p4 were used.
Within this age range, only specimens in comparable pelage
were used to ascertain differences in color.

Miss Viola S. Schantz of the United States Fish and Wildlife
Service, Mr. Alfred Bailey of the Colorado Museum of Natural
History, Dr. W. H. Burt of the Museum of Zoology of the
University of Michigan, Dr. Stephen D. Durrant of the Museum
of Zoology of the University of Utah, Dr. Robert M. Stabler,
curator of the Warren Collection of Colorado Col