ALLEN: AMERICAN COLLARED LEMMINGS. 



511 



All the species turn white in winter, so that for any study of geo- 

 graphic variation in color, only those specimens that have acquired 

 the full summer coat are of value. Until very recently there have 

 been few such specimens available in i\.merica, so that no compari- 

 sons of color have hitherto been made except between the Labrador 

 species and its neighbor on the west side of Hudson Bay. This 

 has continued to obscure our conception of the relationships of the 

 different forms. I 



By way of summary, the Labrador Lemming, D. hudsonim, is found 

 to be a species distinct from any of the Old or New World forms, and 



Fig. 1. — Distribution of the American Collared Lemmings. 1. Dicrostonyx hudsonius 

 (Pallas). 3. D. rubricatus (Richardson). 3. D. r. richardsoni Merriam. 4. D. r. 

 unalascensis Merriam. 5. D. exsul G. M. Allen. 6. D. groenlandicus (Traill). 



is confined to the Labrador Peninsula and the immediately adjacent 

 islands. Its tooth-structure is less complex than that of the other 

 known Collared Lemmings, and the young in summer are hardly differ- 



