36 
No. 79 is identified by H. S. Swarth as L. r. dixoni. It is the yellowest 
and on the whole the darkest of this group, though the difference between 
it and No. 83 is not great and is considerably less than is often caused by 
individual variation in the species. No. 80 is a bird that seems far from 
its natural range, but the date suggests that it might be an early migrant. 
On the whole it seems evident that there are two principal races of 
rock ptarmigan in North America, a yellow northern and a grey southern 
one. On laying these specimens down on the accompanying map (Figure 
1) in appropriate symbols the general trend is evident. There are generally 
well-defined yellow northern and grey southern groups. The dividing 
line between them seems to run from the general vicinity of the Alaska- 
Yukon-British Columbia corner eastward and a little north, just below 
Coronation gulf and across central Baffin island to Greenland near Disko 
island. 
The Newfoundland welchi is indistinguishable from the grey mainland 
bird and western kelloggae is identical with the yellow one, a conclusion 
also reached by Swarth (an tea). There are several occurrences which 
disturb this fair arrangement. Both yellow and grey forms are represented 
in our collection from northern British Columbia, the Yukon coast, west 
Banks island, central Baffin island, Ungava bay, and Disko, Greenland. 
Most of these may be dismissed as migrants, others as individual variants 
or carrying misinterpreted characters. The case of the pale sand-coloured 
birds is very puzzling. Schipler (Dansk Ornithologisk Ridsskrift, 19, 1925) 
restricts reinhardi to the west coast of Greenland, latitude 64 degrees and 
southward. He describes it as very light coloured, light grey on back. This 
agrees fairly well with No. 74, taken at Sukkertoppen, Greenland, latitude 
65° 30', if “light sandy” is substituted for the translation of “light grey.” 
He distinguishes the birds from latitude 66° to 71° as distinct from rein- 
hardi and assumes them to be rupestris. His description in the translation 
available to me is not very clear, but I gather that they are “darker and 
warmer” than reinhardi . This would fit either our northern or southern 
continental forms, but considering we have birds unmistakably of the 
northern yellow type from Disko, and that the general trend of the land 
masses it inhabits is towards north Greenland, it seems safe to infer that 
the bird of northwestern Greenland is the same as those of the adjacent 
northernmost islands. 
The sandy birds of group IX are undoubtedly reinhardi, but what to 
call the sporadic specimens 76, 77, and 78 that seem identical with them 
is a puzzling question. Such a discontinuous distribution as seems inferred 
would be too extraordinary to be accepted on the few specimens at hand. 
One alternative is that the northern race is dichromatic, with a light phase 
dominant in southwestern Greenland and a dark one dominant elsewhere. 
Until further data is forthcoming the question must remain open and sub- 
ject to conjecture. 
The southern grey form is undoubtedly rupestris (type locality Hudson 
bay). For the northern yellow one kelloggae (type locality Prince William 
sound, Alaska) seems to be the next available name, hence we have the 
following principal races and distributions: 
