170 U. Ss. P. R. R. EXP. AND SURVEYS—-ZOOLOGY—GENERAL REPORT. 
in the European P. erminea. Their projection beyond the vertebrz is about one-fifth of the 
length of the caudal vertebra. 
The feet are large, the claws well developed. As usual there are ten naked balls on the fore 
feet, and nine behind. The under surfaces of the feet are sparsely covered with hair, as is 
generally the case with the weasels in summer. 
The predominating color of this species above is of a yellowish chestnut brown, considerably 
lighter than in the P. noveboracensis, and much resembling the colors of P. frenata and 
xanthogenys. From these, however, it is easily distinguished by the absence of light patches on 
the cheeks and forehead. 
The under parts are of a pale brownish yellow ; nearly white about the chin and cheeks, and 
more vividly yellow along the thighs. The line of separation between these colors is quite 
indistinct ; indeed the bases of the hairs above, and the whole of the subjacent fur are yellowish, 
like the belly, the chestnut tinge being imparted by the tips of the hairs. As far as can be 
traced in this uncertainty of outline, the darker color extends on the outside of the arm only to 
about the elbow; the remainder of the fore leg being like the belly; on the hind feet it extends 
along the outside of the limbs to the toes, the upper surface of the feet being yellowish. The 
upper surface of the tail is like the back; beneath it is yellowish chestnut, darker than the 
belly ; the tip for about two inches is lustrous black ; the color commencing not much posterior 
to the end of the vertebre. 
The line separating the colors of the upper and under sides passes quite high up on the flanks; 
the paler portion occupying fully two-fifths of the entire circumference around the middle of the 
body. On the neck it occupies fully three-fifths of the circumference. The white of the cheeks 
extends horizontally along the upper lip to the nostrils; passing under the eye, at a distance 
about half way between the eye and the mouth. 
As stated, this specimen is of very large size. When fresh, the head and body measured 124 
inches ; as a preserved skin, with no unusual amount of stretching, it is rather more than 15 
inches ; the tail vertebrae now measure 53 inches ; with the hairs, 7} inches. These dimensions 
are considerably larger than in the P. noveboracensis. The end of the skull is much broader 
than in this species or in the ermine of Europe, although the teeth are of the same size (more 
widely separated). The posterior upper molar is even narrower than in skulls of P. novebora- 
censis, of much smaller size. Its much lighter tints above, and the greater extent of the paler 
color of the under parts, (over all the legs, beneath the base of the tail, upper lip, &c.,) with 
the stiffer hairs, as well as its size, distinguish it from the other described American ermines. 
The tail is much longer and with a shorter brush than in the Europeanermine. In some respects 
it resembles the P. nigripes, Audubon and Bachman, but is smaller, has a longer tail, is 5 without 
the black of the head and feet, &c. 
The specimen described was taken on Milk river, upper Missouri, by Dr. Suckley, in August, 
1853. Whether it turns white in winter is not known. 
