518 bulletin: museum of comparative zoology. 



west coast of the Labrador Peninsula, Mr. O. J. Murie has lately 

 taken hudsonius at several points from Great Whale River northward, 

 as well as on the Belcher Islands adjacent to that shore. 



Remarks. — This species is so very distinct from all the others of 

 the genus in its dental characters and its color, that I have regarded 

 the differences as of subgeneric value. The resemblance of the 

 young to the adult in summer, as well as the simpler condition of its 

 enamel pattern, may indicate a less degree of specialization. Its 

 geographic range is isolated, and there is no evidence that it inter- 

 grades with the nearest related forms. 



The specific name is credited to Forster by Richardson, but though 

 Forster mentions "a small animal called a Field Mouse" sent from 

 Churchill River and describes its dark median line, he does not name 

 it. Doubtless it was the race now known as richardsoni. Although 

 successively placed in various murine genera by the earlier authors, 

 this lemming seems to have escaped specific synonyms. 



In the series examined, a single specimen (M. C. Z. 8,671) shows 

 an interesting progressive variation in the development of a very 

 small antero-internal accessory enamel fold in the last lower molar, 

 a feature which is characteristic of the subgenus Misothermus. 



Specimens examined, 41, from the following localities: — 



Labrador. 



Hamilton Inlet, Rigolet, 3 (M. C. Z.). 



Indian Harbor, 1 (M. C. Z.) skull only. 



Hopedale, 1 (U. S. N. M.). 



Nain, 4 (M. C. Z.), 4 (Carnegie Mus.). 



Okak, 3 (M. C. Z.). 



Rama, 6 (M. C. Z.). 



Fort Chimo, 4 (U. S. N. M.). 



PortBurwell, 1 (M. C. Z.). 



Nastapoka River, 6 (Carnegie Mus.). 



Richmond Gulf, 1 (Carnegie Mus.). 



Hopewell Sound, 1 (U. S. Biol. Surv.). 



Great Whale River, 4 (Carnegie Mus.). 



Belcher Islands, Hudson Bay, 2 (Carnegie Mus.). 



DiCROSTONYX RUBRIC ATUS (Richardson). 



Alaskan Collared Lemming. 



Arvicola ruhricatus Richardson, Zool. Beechey's voyage, 1839, p. 7. 

 Hypudaeus ruhricatus Schinz, Synopsis Mamm., 1845, 2, p. 250. 



