OCT., 1900.] MAMMALS OF THE YUKON REGION". 37 



widely expanded anteriorl}^, rapidl^^ becoming- eonipressed posteriorly; 

 angular process of mandible short, blunt, and upturned; condyle 

 narrow and somewhat rounded. 



Memm^ements. — Tj'pe (from dry skin): Total length 4:95; tail verte- 

 brne 170; hind foot 73. Skull of type: Basal length 57; zygomatic 

 breadth 38; leng^th of nasals 21; alveolar length of molar series 14. 



Reiiim'Ji's. — Specimens of this species from Ugashik, Fort Kenai, 

 Nushagak, and Nulato, in Alaska, have been examined. Besides 

 these, I find two specimens from Alberta which seem to be referable 

 to it, one from South Edmonton and one from Henry House. These 

 all agree in having very small molar teeth and short, spatulate nasals, 

 characters which are amply sufficient to distinguish the species from 

 all other forms in the genus. The specimens secured by Nelson at 

 St. Michael can not now be found, l)ut they doubtless show the same 

 characters. Fiher osoyooseoisis has larger teeth and a much longer 

 rostrum than spatalatus, so need not be further compared with it. 

 From these facts it appears that Fiher .^patulatux is the form occupying 

 all of northwest America, and is derived from a form east of the 

 Rocky Mountains rather than from a western one. 



Muskrats occur sparingly all along the Yukon, where they find par- 

 ticularly favorable environment about the many small swamp-invested 

 ponds a short distance from the river banks. At St. Michael a few 

 are still found about the open ponds on the tundra. 



Synaptomys dalli Merriam. Dall Lemming Mouse. 



Lemming nnce were taken at the foot of Lake Lebarge, at Rink 

 Rapids, and near the mouth of the Chandindu River. At Lake 

 L('])arge they were found in the long grass at the edge of a small pond; 

 at other localities in cold, boggy places near small streams. The 

 external characters of B. daUl have been unknown up to the present 

 time, but, as was to be expected, they are in accordance with the gen- 

 eral type so uniform throughout this genus. The color of the upper- 

 parts is chiefly raw umber mixed with black; the lower parts are uni- 

 form bluish white, and the feet and tail are dusky. The ears are of 

 medium size and partially hidden by long hairs growing from the 

 aiiterior base; a conspii-uous l)luish-white side gland is present in the 

 males. The skull of the type of dalll is not fully mature and does 

 not agree in all particulars with my specimens from the Upper Yukon. 

 In these the skull is somewhat larger and heavier and the nasals ore a 

 trifle longer and more noticeably constricted posteriori}". 



Lemmus yukonensis Merriam. Yukon Lemming. 



ic»imus 7/w^-o?ie?iS('s Merriam, Proc. Wash. Acad. Sci., II, 27, March 14, 1900. 



This lemming was found at only two localities — Rink Rapids, where 

 five specimens were secured, and Charlie Creek, where five more were 



