336 BACKBONED ANIMALS. 
head (frontal) bone 
of the skull form the 
cores that are cov- 
ered by the horns, 
that are special de- 
velopments of the 
outer skin or epi- 
dermis. 
Goats and 
Sheep.—In the 
Rocky Mountain 
sheep, or big-horn 
(Fig. 359), the horns 
are extremely pow- 
erful. In the fe- 
male, the horns are 
straight, and similar to those of a goat. Their height at 
the shoulder is about three feet, and their weight three 
hundred and fifty pounds. They are now confined to the 
country west of the Missouri, and are fast becoming extinct. 
About forty varieties of the domestic sheep are known. 
Its origin is obscure, 
but it is possibly a 
descendant of an 
Asiatic sheep (Ovzs 
argalt), The Bar- 
bary sheep, or AZou- 
fion, has soft hair 
of a reddish tinge. 
From it and the Si- 
berian Argaid spring 
the merino sheep of 
the East ; their tails 
attain a weight of 
one hundred pounds, : ; 
and have to be sup- FIG. 360,—Musk-sheep (Ovzbos moschatus), 
montana). 
YR 
