SCIURID2E— SPEKMOPIIILUS 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. tridecemlineatus arc 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. 98G, from Racine, the sides of the neck, shoulders, 

 and the breast are sirongly 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 

 thepictura 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. 



Vakietal chars. — Length to base of tail 5.75 to 6.75; of tail- vertebrae 

 2.75 to 3.50; of tail to end of hairs 3.50 to 4.25. Smaller; above paler, 



