484 ROCK GROUS. 
unaltered winter plumage. In this respect the species differs from the 
Willow Grous, whose males first assume the summer colour. The 
Rock Grous is found also on Melville Peninsula and the Barren 
Grounds, seldom going farther south in winter than latitude 63° in the 
interior, but descending along the coast of Hudson’s Bay to latitude 
58°, and in severe seasons still farther to the southward. It also oc- 
curs on the Rocky Mountains as far south as latitude 55°. It exists in 
Greenland, is common in Norway, is known in Sweden by the name of 
Sno Rissa, and is the species most frequent in the Museums of France 
and Italy under the name of TZetrao Lagopus. It is not a native of 
Scotland. The Rock Grous in its manners and mode of living resem- 
bles the Willow Grous, except that it does not retire so far into the 
woody country in winter. Contrary, however, to what HeaRNE says, 
it is frequent in open woods on the borders of lakes in that season, 
particularly in the 65th parallel of latitude, though perhaps the bulk 
of the species remains on the skirts of the Barren Grounds. It hatches 
in June. The ground colour of the egg is, according to Captain 
SaBINE, a pale reddish-brown, and is irregularly spotted and blotched 
with darker brown.” Specimens in my possession, coloured as here 
described, average one inch and five-eighths in length, by an inch and 
an eighth in breadth. 
TETRAO RUPESTRIS, Gel. Syst. Nat. vol. i. p. 731.—Lath. Ind. Ornith. vol. ii. 
p. 640. 
Terrao (Lacorus) rupesrris, Richards. and Swains. Fauna Bor.-Amer. vol. ii. 
p. 354. 
Rock Grovs, Nuttall, Manual, vol. ii. p. 610. 
Adult Male in Winter. Plate CCCLXVIII. Fig. 1. 
Bill short, robust ; upper mandible with the dorsal outline curved, 
the ridge and sides convex, the edges overlapping, the tip declinate, 
thin edged, but rounded; lower mandible with the angle short and 
wide, the dorsal line convex, the back broadly convex, the sides round- 
ed, the edges inflected, the tip blunt. Nostrils basal, roundish, con- 
cealed by feathers. 
Head small, ovate ; neck of moderate length ; body bulky. Feet of 
_ ordinary length, robust ; tarsus feathered, as are the toes, the first toe 
very small, the middle toe much longer than the lateral, which are 
