TETRAONIN^E. TETRAO. 239 



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 LXXXIL TETRAO. 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 



