106 THE AMERICAN NATURALIST. [VoL. XXXV. 
the question. Altogether this species is not found in most of 
the truly Arctic regions, as it is absent, not only in the above- 
mentioned islands, but also in Novaya Zemlya, Francis Joseph 
Land, Taimyr Land north of 72°, New Siberian Islands, Wran- 
gel Land, and the Aleutian Islands. Its northern limit conse- 
quently agrees almost exactly with that of the wolverine (Gulo) 
which Dr. Scharff counts among the Siberian invaders. 
With regard to the Tundra ptarmigans (Lagopus rupestris and 
mutus) our knowledge is unfortunately not quite so complete, 
owing to the difficulty of distinguishing correctly between these 
two forms; but, as Palmén has already indicated, it is highly 
probable that the latter does not occur east of the White Sea, 
that in fact it is confined (with its local races) to the Scandi- 
navian mountains with their Lapland spurs, Scotland, the Alps 
and the Pyrenees, while Z. rupestris (with its various forms and 
subspecies) extends over the entire Siberian and North Ameri- 
can Tundra and Barren Ground, as well as Spitsbergen, Green- 
land, and Iceland. The former, therefore, is nearly uniform in 
its distribution with Myodes lemmus, while the latter corre- 
sponds fairly well to that of A. odensis (and its local forms). 
The significant fact in this connection, in so far as the ptarmigans 
are concerned, is that both the Spitsbergen, the Greenland, 
and the Iceland forms belong to the Siberian and American 
L. rupestris, while the Scandinavian and Scotch (also probably 
subfossil English and Irish) ptarmigans, with those of Switzer- 
land and the Pyrenees, form the Z. mutus group. These, 
therefore, cannot have come from America via Greenland and 
Spitsbergen (or Iceland). 
But while thus this group of animals, which Dr. Scharff has 
called Arctic immigrants, by both physical and distributional 
reasons is barred from the route America-Greenland-Spitsl 
Norway-Scotland-western Europe, it may be partinently asked, 
By what road did they reach western Europe, Scotland, and 
Norway ? 
Let us first determine where they did not come from. 
Having eliminated Greenland and Spitsbergen, there are to 
the northward only two countries which need be further 
investigated, vis., Norway and Iceland. 
