Assuming that in its circumpolar origin the North Temperate flora was fairly homogeneous, it would meet in its centrifugal extension with a wide range of local conditions; these would favor the preservation of numerous species in some genera, their greater or less elimination in others.
The narwhal is an Arctic whale, frequenting the icy circumpolar seas, and rarely seen south of 65° N.
Of the sixty-one species of birds breeding in Greenland, eight are European-Asiatic, four are American, and the rest circumpolar or North Atlantic and North Pacific in their distribution.
The circumpolar lemmings of the genera Lemmus and Dicrostonyx are noticed in the article Lemming.
Nigripes; while the circumpolar banded lemming, Dicrostonyx torquatus, which turns white in winter, represents a second genus taking its name from the double claws on one of the toes of the forefeet.
From 1855 to 1859 he acted as director of the Dudley observatory at Albany, New York; and published in 1859 a discussion of the places and proper motions of circumpolar stars to be used as standards by the United States coast survey.
A few, on the other hand, have a very restricted range, the Greenland right whale (Balaena mysticetus) being, for instance, limited to the zone of the northern circumpolar ice, while no corresponding species occurs in the southern hemisphere.