DICROSTONYX. 



Fig. 48. DiCROSTONYx huosonius nelsoni. 



No. 2go Field Columbian Museum Coll. Nat. size. 



Lower tooth row. 

 Enlarged 4 times. 



Upper tooth row. 



Enlarged 4 times. 



Genl. Char. Ears hidden in fur, four claws on front feet, tail and 

 legs very short. 



Color. Summer Pelage. Above ash gray mixed with reddish and 

 blackish brown; lower parts rufescent; a lateral line from sides of face 

 and neck dividing the colors of upper and under parts, dark brown. 

 Grayish black streak from nose to nape; sides of head gray; whiskers 

 brown or white. 



Winter Pelage. Pure white. 



Measurements. Total length, 140; tail vertebrae, 13; hind foot 

 and claw, 20; fore foot and claw, 28; longest claw, 10. 



a.~unalascensis. {Dicrostonyx^, Merr. , Proc. Wash. Acad. Scien., 

 1900, p. 25. 



Type locality. Unalaska, Alaska. 



Genl. Char. Size rather large. Skull alone known. This is 

 large and broad with subquadrate brain case, broadly spreading 

 rounded zygomata, broadly sulcate frontal, and prominent peg-like 

 postorbital processes of squamosal. First upper molar with three 

 closed interior triangles and posterior loop; and second upper molar 

 with second interior loop normal, and separated by full interspace 

 from anterior crescent of third upper molar, and posterior loop com- 

 plete. (Merr.) 



b. — nelsoni. {Dicrostonyx), Merr., Proc. Wash. Acad. Scien., igoo, 



P- 25- 



alascensis. Stone, Proc. Acad. Nat. Science Phil., 1900, p. 37. 



Type locality. St. Michaels to Point Barrow, Alaska. 



Genl. Char. Size rather small. Audital bullae very small and 

 narrow; incisive foramina short; molars small and narrow. Upper 

 parts chestnut; feet white. 



