486 ROCK GROUS. 
black, and the tail is black as in winter, tipped with white, and with 
the lateral feathers having part of their outer web white ; the two mid- 
dle feathers barred like the back. ‘The dimensions of an individual are 
as follows : 
Length to end of tail 134 inches, to end of wings 114; wing from 
flexure 74; tail 43; bill along the ridge 7% ; tarsus 154; middle toe 34, 
its claw ;5. 
Female in Summer. Plate CCCLXVIII. Fig. 3. 
The female does not differ materially from the male, the yellow 
bands being only broader and lighter. 
Very great differences are observed in the length and form of the 
claws, they being in some individuals very long, thin-edged, and ta- 
pering, to a rounded point ; in others very short, being worn down to 
the stump. ‘This species is considerably smaller than the Ptarmigan 
of Scotland, which it precisely resembles in its winter plumage. In its 
summer plumage, however, it differs in having the markings larger ; 
and as yet no specimens have been obtained marked. with undulated 
slender, ash-grey, and dusky lines, in any degree approaching those 
characteristic of the British bird in its autumnal plumage. The bill 
of the Rock Grous is shorter and thicker than that of the Ptarmigan, 
although the reverse has been alleged. 
