MAMMALS OF MINNESOTA . 287 
layers, the transformation of which produces the horney por- 
tion, lies directly upon the periost of the core. The hairs 
which cover the skin, enveloping the core before horn is 
formed persist, and thus, according to Prof. Curtis, assist in 
tying down the horny shell. Upon the way in which the epi- 
dermis is altered to form horn, I may again be permitted to 
quote from Caton’s excellent work: ‘‘ Now, the peculiarity 
about this is, not that the epidermis is the source of the horn, or 
is converted into horn, but that a very limited section should 
be stimulated to extraordinary activity till its work is accom- 
plished, and then subsides into a comparatively dormant state; 
and then another portion wakens to the same vigorous action, 
to be again succeeded by another active section still lower 
down; this state of activity, commencing at the top of the core 
and eradually passing along down it, followed by the per- 
fected horn, and the quiet condition of the epidermis lining its 
cavity; and that this extraordinary phenomenon should occur 
annually.” 
Having thus fully discussed the horns, it remains to mention 
the other prominent and interesting appendages, the hoofs. 
The Prong-horn is one of the few ruminants which externally 
are bi-digitate. This may be taken as an indication of extreme 
development in an old type, and expresses the greatest extreme 
of reduction in the artiodactyle series, as the horse does in the 
perissodactyle. The hoofs are similarly shaped on both feet, 
and are very acute and narrow. The external margin is some- 
what concave. 
The tail is short, measuring little more than three inches. 
The hair is coarse, somewhat crinkled, stiff and quite brittle. 
It shows no tendency to felt or mat, but bristles coarsely and us- 
ually rather raggedly over the body. There is little or no under 
fur in summer, but according to Caton this is present in consider- 
able quantities in the colder season. The neck is clothed with 
a stiff bushy mane, of which the hairs may be four inches long. 
The brittle character of the pelage unfits the fur for robes, but 
although weak, the skin is said to rival chamois skin for like 
purposes. 
The color seems to be very uniform, the variations being 
chiefly such as are incident to exposure and slight seasonal 
modification. The colors are bright and striking, and so well 
marked that they are easily recognized, as may be seen by com- 
paring the subjoined rudesketch by an Indian with our plate. 
The prevailing color is rufous yellow to tawny. The face is 
