16 University of California Publications in Zoology — | Vou. 17 
while in nelsoni the hue is close to ight pinkish emnamon, approach- 
ing whitish back of ears. A tendency is observable in amplus to have 
the white of the lateral stripes a little obscured by an admixture of 
light buffy hairs, particularly towards the rump. In nelsoni the 
stripes are purer white. The general pallor of amplus also renders 
the white stripes less conspicuous. The white eye-ring is also less 
prominent in amplus than in nelsom. The pure coloration of the 
upper surface of fore and hind lmbs tends toward pinkish buff in 
amplus, more towards light pinkish cmnamon in nelsoni, although in 
certain examples no difference in hue is appreciable. There seems 
to be a tendency in amplus toward a flatter tail than in nelsoni. 
The coloration of the tail seems also to be more clearly disposed in 
bands than it is in nelsoni, im which the tail dorsally is more indis- 
criminately mixed, blackish and whitish. 
There are no conspicuous cranial differences between the two 
forms. Certain crania of Ammospermophilus nelsoni amplus average 
2.7 per cent longer than in A. n. nelsoni, mastoid width about 3.0 
per cent greater, and nasals about 9.8 per cent longer. 
Difference in size usually furnishes a comparatively conspicuous 
character. Total length in Ammospermophilus nelsoni amplus aver- 
ages 9.6 per cent above the average in A. n. nelsoni; length of tail 
vertebrae, 5.4 per cent, length of hind foot, 6.0 per cent, and length 
of ear, 40.8 per cent. Unfortunately the length of ear cannot be 
measured, by the methods used, accurately enough to be as reliable 
as are the other measurements. 
With two exceptions the specimens of Ammospermophilus nelsoni 
amplus are im summer pelage. Two examples (nos. 13816, 13817, 
Mus. Vert. Zool.), taken March 25 and March 27 respectively, are 
in winter coat. The pelage in winter is softer and thicker than in 
summer, and is more grizzled or spotty; hues of coloration are paler, 
and the white stripes on the sides less conspicuous. One of the 
examples (no. 13816) is inclined more toward grayish or whitish; 
the other (no. 13817) is more yellowish. 
Distribution.—Of Ammospermophilus nelsoni amplus there are 34 
specimens (including three skeletons-only) in the Museum of Verte- 
brate Zoology, representing two localities, as follows: Sweeney’s 
Ranch, 22 miles south of Los Banos, California, 2; mouth of Little 
Panoche Creek, 18 or 20 miles south of Los Banos, 32. 
Remarks.—Although Ammospermophilus nelsoni amplus is a well- 
marked form, it is sufficiently close to A. n. nelsoni to be referred to 
