470 ZOOLOGY. 
Missouri and the prairie towns; thence to the Platte they were much 
more numerous. ‘The entrance to the burrow is at the summit of the little 
mound of earth brought up by the animal during the process of the excava- 
tion below. These mounds are sometimes inconspicuous, but generally 
somewhat elevated above the common surface, though rarely to the height 
of eighteen inches. Their form is that of a truncated cone, on a base of 
two or three feet, perforated by a comparatively large hole or entrance at 
the summit or in the side. The whole surface, but more particularly the 
summit, is trodden down and compacted, like a well worn pathway. The 
hole descends, vertically, to the depth of one or two feet, whence it con- 
tinues in an oblique direction downwards. <A single burrow may have 
many occupants. We have seen seven or eight individuals sitting upon 
one mound. The burrows occur usually at intervals of about twenty feet. 
They delight to sport about the entrance of their burrows in pleasant 
weather. At the approach of danger they retreat to their dens, or when its 
proximity is not too immediate, they remain, barking and flourishing their 
tails, on the edge of their holes, or sitting erect to reconnoitre. When 
fired upon in this situation, they never fail to escape, or, if killed, to fall 
into their burrows, where they are beyond the reach of the hunter. As 
they pass the winter in a lethargic sleep, they lay up no provision of food 
for that season, but defend themselves from its rigors by accurately closing 
up the entrance of the burrow. The further arrangements which the 
prairie dog makes for his comfort and security are well worthy of attention. 
He constructs for himself a very neat globular cell with fine dry grass, 
having an aperture at the top large enough to admit the finger, and so 
compactly formed, that it might almost be rolled over the floor without 
injury.” 
The genus Zamias (the ground squirrels) is very nearly allied to the 
squirrels proper (Sciurus), from which it differs by many particulars, among 
which is the presence of ample cheek-pouches, a longer head, the ears placed 
further back, a more slender body, and shorter extremities. The ears 
themselves are rounded, and without any tufts on the edge or behind them. 
The tail is shorter than the body, rounded, narrow, seldom turned up. 
There are four toes to the fore feet, with a minute blunt nail in place of a 
thumb, and five to the hind ones. The claws are hooked. ‘T'wo incisors 
above and two below, smooth, the lower ones compressed and sharp. The 
molars are five above and four below on each side, short, and the .crown 
tuberculous. The species are all of small size, and longitudinally striped on 
the back and sides. They do not mount trees unless driven thither by 
necessity, but dig burrows, and spend their nights and the season of winter 
under the ground. 
Several species of this genus exist in North America; one is known in 
South America, and another in the northern portions of the eastern con- 
tinent. The chipping squirrel or hackee (Zamias lystert) is found from 
the northern lakes (Huron and Superior) all along the eastern, northern, 
and middle states and range of Alleghany Mountains. 
The genus Seiwrus is characterized by an elongated body; a long tail, 
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