June 7,1924 
Variation in Microtus Montanus Yosemite 
997 
Table IV .—Measurements of the skulls of females (in millimeters) 
Collection number 
Condylo-basilar 
length 
C ondylo-zy gomat- 
ic length 
Alveolo-basilar 
length 
Condylo-palatal 
length 
Zygomatic width 
Interorbital width 
Lambdoidal width 
: 
Height 
Tooth row 
Incisive foramina 
Alveolar width 
Nasals 
Angular process 
3815.— 
27.6 
22.9 
16.2 
12.5 
17.0 
3.9 
12.8 
11.1 
6.9 
5.6 
5.7 
8.5 
5.5 
3856.. 
27.4 
22.8 
16.2 
13.0 
16.5 
3.9 
12.8 
11.2 
6.9 
5.5 
5.8 
8.3 
5.2 
3865... 
26.9 
22.2 
15.9 
12.9 
16.0 
3.6 
12.4 
10.8 
7.1 
5.6 
5.8 
8.2 
5.2 
3819___ 
26.9 
22.2 
16.5 
12.3 
17.1 
3.7 
12.7 
10.9 
7.2 
5.5 
5.9 
8.3 
5.5 
3844. 
26.8 
22.3 
15.8 
12.3 
17.6 
3.7 
13.1 
11.1 
7.0 
5.7 
6.0 
8.3 
5.7 
3871 ... 
26.8 
22.1 
15.3 
13.1 
15.9 
3.7 
12.4 
10.7 
6.7 
5.5 
5.7 
7.6 
6.1 
3816... 
26.8 
22.0 
15.7 
12.5 
15.9 
3.7 
12.1 
10.6 
6.6 
5.3 
5.6 
8.0 
6.2 
3845... 
26.8 
22.3 
16.1 
12.0 
16.6 
3.8 
12.6 
10.9 
7.0 
5.3 
5.8 
8.3 
5.6 
3817..-.- 
26.7 
21.7 
15.5 
12.8 
15.9 
3.6 
12.3 
10.6 
6.6 
5.4 
5.5 
7.9 
5.6 
3884... 
26.7 
22.0 
16.2 
12.3 
16.4 
4.1 
12.8 
11.0 
7.3 
5.3 
5.6 
8.0 
5.2 
3836-... 
26.7 
22.2 
15.6 
12.7 
16.8 
3.9 
12.2 
10.3 
7.4 
5.2 
5.8 
7.8 
5.7 
3881--... 
26.4 
21.7 
15.9 
12.1 
16.5 
3.9 
12.3 
10.9 
6.9 
5.5 
5.8 
7.7 
5.5 
3877-... 
26.0 
21.3 
15.8 
12.1 
16.1 
3.6 
12.4 
10.5 
7.0 
5.0 
5.9 
7.4 
5.1 
3863-_..- 
25.8 
21.5 
16.0 
12.1 
16.8 
4.0 
12.3 
11.0 
7.2 
5.5 
5.7 
7.7 
5.5 
3869... 
25.8 
21.2 
15.1 
12.1 
15.4 
3.8 
11.7 
10.7 
6.4 
5.1 
5.5 
7.7 
5.2 
3876..... 
25.7 
21.2 
15.3 
12.2 
16.6 
3.7 
12.3 
10.6 
6.6 
5.5 
5.7 
7.5 
5.6 
3831_ 
25.7 
21.1 
15.6 
12.1 
15.8 
3.9 
12.3 
10.6 
6.9 
5.4 
5.4 
7.4 
5.6 
3821-.. 
25.6 
21.4 
15.2 
11.8 
15.4 
3.9 
11.9 
10.6 
6.5 
5.5 
5.4 
7.4 
5.0 
3840. ..... 
25.5 
21.2 
15.1 
1L 5 
15.2 
3.8 
11.9 
10.5 
6.4 
5.4 
5.6 
7.3 
5.0 
3880. ___ 
25.5 
21.4 
15.2 
12.5 
15.5 
4.0 
12.0 
11.1 
6.6 
5.5 
5.6 
7.5 
5.4 
3830-__ 
25.5 
21.5 
15.0 
11.8 
15.1 
3.8 
11.9 
10.8 
6.5 
5.4 
5.4 
7.4 
5.2 
3827...... 
25.4 
21.7 
14.6 
12.1 
15,9 
4.0 
12.2 
11.0 
6.6 
5.2 
5.5 
7.2 
5.3 
3828. ____. 
25.4 
20.9 
15.1 
11.8 
15.0 
3.7 
11.9 
10.5 
6.0 
5.3 
5.4 
7.8 
4.7 
3872.... 
25.4 
21.2 
15.0 
12.2 
15.1 
3.7 
11.8 
10.8 
7.4 
5.3 
5.6 
7.5 
5.4 
3838.... 
25.4 
20.9 
15.1 
12.1 
15.0 
3.6 
11.7 
10.8 
6.2 
5.2 
5.4 
7.5 
4.7 
3850. ... 
25.2 
20.8 
14.8 
11.7 
14.6 
3.7 
11.6 
10.4 
6.7 
5.3 
5.6 
7.1 
4.7 
3885.... 
25.1 
20.7 
15.2 
11.8 
15.4 
3.9 
12.0 
10.6 
6.9 
5.6 
5.6 
7.0 
5.0 
3886... 
25.0 
20.7 
14.6 
11.3 
15.1 
3.8 
11.4 
10.9 
6.1 
5.3 
5.6 
7.0 
5.1 
3873.. 
24.9 
21.2 
14.7 
12.2 
15.0 
3.6 
11.2 
10.6 
6.6 
5.0 
5.5 
7.0 
5.2 
3813__ 
24.9 
21.0 
14.8 
11.9 
14.6 
3.6 
11.5 
10.1 
6.8 
5.8 
5.4 
7.4 
4.7 
3882..__ 
24.9 
21.2 
14.9 
11.5 
14.8 
3.8 
11.9 
10.5 
6.7 
5.2 
5.4 
7.1 
4.8 
3839.... 
24.9 
20.7 
14.7 
11.3 
14.3 
3.6 
11.4 
10.3 
6.4 
5.4 
5.4 
7.1 
4.7 
3852.. 
24.8 
20.6 
14.7 
11.2 
15.3 
3.8 
11.7 
10.3 
6.4 
5.2 
5.5 
7.3 
5.0 
3829... 
24.7 
20.5 
14.9 
11.5 
14.7 
3.7 
11.6 
10.2 
6.5 
5.4 
5.4 
7.4 
4.7 
3842.. 
24.6 
20.5 
14.7 
11.4 
14.8 
3.6 
11.4 
10.5 
6.3 
5.1 
5.4 
6.9 
4.9 
3861__ 
24.6 
20.3 
14.6 
11.5 
15.0 
3.6 
11.4 
10.5 
6.4 
5.0 
5.4 
7.2 
5.0 
3866_ 
24.6 
20.3 
14.8 
11.3 
15.2 
3.6 
11.4 
10.6 
6.5 
5.5 
5.3 
■6.8 
5.1 
3851.. 
24.5 
20.6 
14.9 
11.7 
15.4 
3.8 
12.0 
10.5 
6.8 
5.1 
5.3 
7.1 
5.0 
3888_ 
23.8 
19.8 
14.5 
11.2 
14.3 
3.7 
11.2 
10.8 
6.6 
5.0 
5.3 
7.1 
4.8 
3832.... 
23.2 
19.5 
14.1 
11.0 
14.0 
3.6 
11.2 
10.0 
6.3 
4.5 
5.2 
6.9 
4.7 
3833..... 
22.3 
18.8 
13.3 
10.2 
13.6 
3.8 
11.2 
9.8 
6.0 
4.1 
5.0 
6.5 
4.5 
a Averages. 
25.7 
21.34 
15.27 
12.0 
15.63 
3. 77 
11.99 
10. 65 
6.7 
5.35 
5.5 
7.5 
5.24 
° Average measurements of 32 (roughly three-quarters) of the skulls of females, the three largest and 
six smallest specimens having been eliminated. 
In lateral profile the skulls of juveniles are evenly rounded, with a sharper curve 
barely perceptible at the posterior portion of the frontals and no undue prominence 
at the anterior margin of these bones. In older animals the dorsal profile is very 
much less rounded. In the larger subadults the greatest prominence has shifted 
to the vicinity of the nasal-frontal suture, while in adults this has increased, with 
considerable angularity and pronounced declivity of the rostrum in many cases. 
There is individual variation of limited extent in this outline and in the exact 
age at which the change is apparent. In transverse outline from a posterior view 
the braincase in juveniles is proportionately higher and therefore narrower, 
and more evenly arched, or in other words, more nearly circular; while in the case 
of adults this outline is much more oval. 
COMPOSITE MEASUREMENTS 
The composite measurements have been as follows: 
Condylo-basilar length. —The average of this measurement for the 19 
intermediate males (see footnote, Table III, p. 996) is 26.2 mm., with extremes 
