^1914^] THAYER AND BANGS — BIRDS 5 



ours. It remains therefore only to compare our bird with the 

 American forms, to one of which the East Siberian ptarmigan has 

 been referred by some ornithologists. 



The two American continental forms (exclusive of L. lagopus 

 alexandrce Grinnell, which differs in color) are L. lagopus alhus 

 Gmelin, of Alaska and arctic America, east to Hudson Bay, and 

 L. lagopus ungavus Riley, of eastern arctic America, Ungava, 

 etc., west to Hudson Bay. These two forms are distinguished only 

 by the eastern having a heavier bill than the western. This char- 

 acter, however, although slight, holds good, and readily distin- 

 guishes the two. 



The arctic East Siberian form, which we consider separable, has 

 a bill as large as the largest-billed American form, L. lagopus un- 

 gavus, larger on the average than in L. lagopus alhus, but differently 

 shaped from theirs. In its shape it resembles that of L. lagopus 

 lagopus of Europe. It is long, the outline of the culmen is straighter 

 than in American birds, and much less abruptly decurved, and the 

 bill is not so deep, measured vertically through the culmen, and 

 therefore quite different in general appearance — much less stubby. 

 The new form also averages a little larger than L. lagopus alhus. 

 In color we can detect no differences. 



Type from Nijni Kolymsk, Kolyma, Siberia, adult cf , no. 64,074, 

 M. C. Z., collected June 12, 1912, by Johan Koren. 



MEASUREMENTS (In millimeters). 



