TETRAONINiE. TETRAO. 
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the dorsal line slightly convex, the edges erect, the tip 
rounded. Tongue triangular, pointed ; oesophagus with 
an excessively large crop ; stomach a very powerful giz- 
zard, having the muscles extremely large, the epithelium 
with two thick concave grinding surfaces ; intestine long 
and wide ; coeca excessively elongated, cylindrical, with 
internal longitudinal ridges, and of greater capacity than 
the intestine. Feet short, stout ; tarsus partially or en- 
tirely feathered ; toes bare or feathered ; hind toe small 
and elevated ; claws moderate or long, arched, obtuse. 
Plumage full, feathers with a large plumule ; wings ra- 
ther short, convex, rounded ; tail of more than twelve 
feathers. A bare papillate fringed membrane over the 
eye, and a bare space on each side of the neck, usually 
concealed. 
These birds belong chiefly to the arctic and temperate 
regions. They feed on twigs, buds, and herbage ; run 
with great speed, and have a direct, heavy, but rapid flight. 
The males in many species are polygamous and com- 
bative. The nest is placed on the ground, the eggs are 
numerous and spotted, and the young covered with stiff- 
ish down. Four species occur in Britain. 
GENUS LXXXII. TETEAO. GROUSE. 
Bill short, strong, slightly curved ; upper mandible with 
its dorsal line nearly straight at the base, toward the end 
arcuato-declinate, the ridge convex, the sides rounded, the 
edges sharp and overlapping, the tip thin-edged and rounded ; 
lower mandible narrower, with the angle broad, the dorsal 
line slightly convex, the back broadly convex, the sides con- 
vex, the edges erect, the tip rounded ; gape-line arched. 
Mouth narrow ; tongue short, triangular, flat above, pointed ; 
oesophagus narrow, with a very large crop ; stomach a power- 
ful gizzard, of a roundish form ; intestine long, rather wide ; 
coeca extremely long, wider than the intestine, and of greater 
capacity. Nostrils basal, lateral, oblong, operculate, con- 
cealed by the short feathers of the nasal membrane. Eyes 
