260 Mammals of Eastern Asia 
for an unknown distance. In the Kolyma River region north- 
west of the Okhotsk Sea, D. chionopccs is found. This last is 
smaller than torquatus, the length of head and body 4y 2 inches, 
tail i/o inch, hind foot % inch. A specimen collected in October 
had already nearly completed its transformation into white 
winter pelage. The color was entirely white except for a patch 
of hazel on the top of the head and nape, and one on the chest. 
The Red-backed or Gray Lemmings, My opus, are a genus 
of relatively unspecialized, thick-set lemming-like Voles, lack- 
ing the bright colors of Lemmus, the collar of Dicrostonyx, and 
the grooved upper incisor teeth of Synaptomys. The ear, though 
small, has a distinct valve to regulate the size of the ear open- 
ing. The feet lack the special features of Lemmus and are 
slender, with no unusual growth of hair. These Lemmings occur 
in the fir forests of northern Eurasia, from Scandinavia to 
eastern Siberia. The typical species is M. schisticolor of north- 
ern Europe. 
In Siberia occur M. middendorfi from the west coast of the 
Okhotsk Sea and M. thayeri from the neighborhood of the 
Kolyma River, north of the former. My opus thayeri is deep 
gray with a mixture of whitish hairs which are dominant on 
the undersurface, a faint tinge of russet on the back, the feet 
silvery drab. A cluster of stiff whitish hairs grows at the wrist. 
In M. middendorfi the red on the back is much accentuated and 
may extend from the forehead to the base of the tail. The head 
of this form is said to be larger than that of M. thayeri. The 
lengths of head and body in M. thayeri are 4% inches, tail % 
inch, hind foot % inch; of middendorfi 3% inches, % inch, 
% inch. 
The True Lemmings, genus Lemmus, have won fame by 
their occasional periods of extraordinary abundance in Scan- 
dinavia, when after eating everything they can find they move 
outward from the center of scarcity which they have created, 
eventually reaching and swimming out into the sea where they 
perish. The ears of Lemmings, though hidden by their long fur, 
