SCIURIDAiX—SPERMOPHILUS TRIDECEMLINEATUS. 873 
brown, varying to nearly black; the white lines rather narrow, about one- 
third the width of the interspaces; sides strongly yellowish, varying to 
yellowish-rufous. 
The specimens referred to var. tredecemlineatus are from the prairie region 
of the Mississippi Valley and northward, and differ from those referred to 
var. pallidus in being much larger and darker. The dark portion of the dor- 
sal surface is decidedly blackish, mixed generally more or less with very dark 
chestnut, but sometimes is clear, quite intense black, as in No. 11545, from 
Turtle Mountain, 49th parallel, and others from Pembina, Dak., Racine, 
Wis., and Northern Illinois. Others, however, from the same localities, show 
considerably more chestnut, some being clear dark chestnut, with very little 
black. The color of the lower surface also varies from pale yellowish-white 
to pale rufous. In No. 986, from Racine, the sides of the neck, shoulders, 
and the breast are strongly yellowish-rufous, and the buttocks brownish- 
rufous. There are generally three and sometimes four narrow but distinct 
and continuous yellowish-white stripes on each side of the median line, alter- 
nating with five broad dark ones, which are from three to four times the 
width of the light stripes. The middle of each dark space is traversed by 
an interrupted line of squarish, sharply-defined, yellowish-white spots, usually 
separated from each other by a dark interval about equalling their own length. 
Along the median line, especially anteriorly, they frequently tend to form a 
continuous narrow light line. Lower down on the sides of the body are one- 
to two other shorter light stripes, more suffused with yellow, and separated 
by a dark space of about their own width, generally without light spots. 
Anteriorly, over the shoulders, the light spots in the dark spaces tend to 
become confluent, forming nearly unbroken light lines, alternating with dark 
ones of about the same width. In such cases, the second light line from the 
middle of the back, on either side, disappears at the shoulder, where the 
interrupted line ceases to be a continuous stripe. Hence, over the shoulders 
the pictura is resolved into seven continuous light stripes separated by broader 
dark ones. In about one specimen in thirty, the markings are irregular and 
the lines all broken and somewhat indistinct. 
Var. PALLIDUS. 
VARIETAL CHARS.—Length to base of tail 5.75 to 6.75; of tail-vertebree 
2.75 to 3.50; of tail to end of hairs 3.50 to 4.25. Smaller; above paler, 
