138 MICROTINiE 



Distribution and Range in time. — Circumpolar. In the Old 

 World it is not known to occur in Lapland, but from the eastern 

 shore of the White Sea its range extends more or less continuously 

 eastwards to the Behring Strait. In this region apparently it does 

 not now come south of latitude 68° N. ; northwards it is known 

 to reach 82° N. latitude, inhabiting Spitzbergen,^ Novaya Zemlya 

 and the New Siberian Islands. Fossil remains of at least two 

 species occur abundantly in the late Pleistocene deposits of 

 Western and Central Europe, indicating that the range of the 

 genus was formerly far more extensive in the Old World than at 

 present, extending southwards and westwards to Ireland, southern 

 England, southern France and the Swiss Alps. Remains of 

 the genus are also known from the late Pleistocene of Central 

 Asia, indicating that its range in that continent formerly extended 

 southwards at least to the Altai Mountains. 



In America the genus ranges through the Labrador Peninsula, 

 the whole of Arctic America from the western shore of Hudson's 

 Bay to Alaska and the islands of St. Lawrence and Unalaska, the 

 Arctic Archipelago, and northern and eastern Greenland. No 

 fossil remains have, as yet, been found in the New World. 



Characters. — Medium-sized Microtinse, sharply distinguished 

 from all other genera by their highly modified external characters, 

 remarkable seasonal changes in the pelage, colour, and fore-claws, 

 peculiar skulls and characteristic cheek-teeth. 



Size medium, hind-foot 15-20 mm., condylo-basal length of 

 skull 29-32 mm. Fur dense, long, very soft and silky. Eyes 

 moderate, larger than in Lemmus. Ears very small, each 

 reduced to a low fold of naked integument encirchng the meatus 

 and entirely concealed beneath the fur ; pre-auricular ear-tufts, 

 formed by hairs arising from the region immediately in front of 

 the meatus, well marked, capable of motion independently of 

 the rest of the fur and serving completely to close the meatus 

 when laid back by muscular contraction. ^ Tail short and 

 cylindrical, its vertebrae about equal to the hind-foot in length, 

 densely clothed with long adpressed bristles, forming a true 

 terminal pencil which often somewhat exceeds the vertebral 



1 No material has been seen from Spitzbergen, but Arctic Lemmings 

 are said by Heuglin to be carried there occasionally by drift ice. Parry 

 found the skeleton of one upon an ice-floe to the north of Spitzbergen 

 in lat. 81° | N. (Appendix to " Narrative," 1828, p. 190.) 



Heuglin says : " In der Advent-Bai im Is-fjord stiess ich iibrigens 

 an giinstigen, sommerlich gelegenen Oertlichkeiten ofter auf Lemmingbaue 

 und unser Harpunier versicherte mich, in derselben Gegend diese Thiers 

 ausgegraben zu haben " (Reisen n. d. Nordpolarmeer, 1870-1871, Theil 3, 

 p. 8, 1874). 



^ The character and independent motion of these ear-tufts have been 

 described by Heuglin (Reisen n. d. Nordpolarmeer, 1870-1871, Theil 3, 

 p. 10, 1874), who had opportunities of examining living examples of D. 

 torquatus. Recently, thanks to the generosity of Mr. E. Else, I have 

 been able to observe a living specimen of D. hudsonius from Labrador, and 

 I am able to confirm HeugUn's statements. 



