OF THE UPPER MISSOURI. 139 
nized as frequenting any portion of the country drained by the Missouri and its tribu- 
taries. 
Several species of quadrupeds represented in the collection do not pass above certain 
limits on the Missouri river. 
The Scalops argentatus has not yet been observed above the mouth of Big Sioux river, 
and it is not probable that it will be seen above the rich bottom lands which extend only 
to the Niobrara; and the mouth of White river may be considered the most northern 
limit of Geomys bursarius ; the Thomomys rufescens, which has not occurred before, seem- 
ing to take its place from thence to the mountains, The Gray and Black Squirrel (Sciurus 
Carolinensis) has not yet passed above the mouth of Big Sioux river, and the S. Ludovi- 
cianus, or Fox Squirrel, reaches its most northern limit near the mouth of White river. 
This is doubtless owing to the absence of trees which bear their favorite food. Although 
a single Otter was taken by our party on the Niobrara river, and is not unfrequently 
caught near the mouth of Big Sioux, it is very seldom, if ever, seen above Fort Pierre. 
The Fisher (Mustela Pennantii) is somewhat abundant along the rivers and streams flowing 
from the north into the Missouri, and the Muskrat (Fiber zibethicus) is very common 
around Council bluffs, and gradually ceases before reaching the Niobrara. I have been 
told by the traders that this animal is occasionally seen along the Missouri near Fort 
Union and on the Yellowstone, but I have never known of any skins being preserved to 
authenticate the statements. 
Sorex Haypent, Baird. 
Hayprn’s Surew. Baird, General Report on Mammals, 1857, p. 29. 
This small species of Shrew must be quite rare in Nebraska. During all my examina- 
tions of that country, I have been able to secure but three specimens, and these are the 
only ones at present known. A single specimen was caught near Fort Pierre, a second 
one at Fort Union, and a third was found dead along the shore of the Missouri river, near 
the mouth of Cannon-ball river, so that as far as we at present know its range is along 
the Missouri from latitude 44° 20’ to 48°. Specific character : Head less than eight-tenths 
of an inch; acutely attenuated. Body about 1 75 hundredths of an inch; vertebre of 
tail 1.25. Tail very thick and swollen; hind feet four-tenths of an inch; teeth pitchy 
chestnut. Color above, grayish chestnut brown ; beneath, whitish ; upper premolar not 
imbricated; 3d and 4th equal and decidedly less than the two anterior. 
BLARINA BREVICAUDA, Gray. 
SHoRT-TAILED SHREW. Baird, General Report on Mammals, 1857, p. 42. 
The only specimen of the above species in our Nebraska collection was discovered near 
Fort Berthold, on the Missouri river, in latitude 474°, longitude 102°. Very rare. 
