APPENDIX F 345 



Lemmus trimucronatus (Richardson). Back Lemming. 



This interesting species, which was described by Richardson 

 from specimens taken at Point Lake, near the head of Copper- 

 mine River, was found by us near our camp at the tree limit on 

 Artillery Lake, and was collected also at the following points to 

 the northward: head of Casba Lake, outlet of Aylmer Lake, 

 north shore of Aylmer Lake and Sandhill Bay. The series col- 

 lected comprise the first specimens taken anywhere in the region 

 of the type locality since the days of Richardson. 



An adult male, taken on the north shore of Aylmer Lake, 

 August 17, measured: length, 158; tail, 24; hind-foot, 20. An 

 adult female, same place and date, contained four embryos. 



Dicrostonyx richardsoni Merriam. Richardson's Lemming. 



A few specimens of this interesting species were collected from 

 the following points : Artillery Lake at the tree limit and the out- 

 let of Aylmer Lake. 



Microtus (Microtus) drummondi (Aud. and Bach.). Drummond 



, Vole. 



Specimens of this widely distributed species were taken at the 

 following points: Near Fort McKay, Slave River, twenty miles 

 below Peace River, Fort Smith, Fort Resolution, north shore of 

 Great Slave Lake, near Mountain Portage, Fort Reliance, Burr 

 Lake, on Pike's Portage, Artillery Lake at the tree limit, and 

 Aylmer Lake (north shore and Sandhill Bay). Specimens con- 

 taining embryos were obtained as follows: Fort McKay, May 31, 

 five large embryos; Slave River, twenty miles below Peace River, 

 5 6 7 embryos, respectively; Fort Smith, June 14, nine large 

 embryos. 



Fiber zibethicus spatulatus Osgood. Northwest Muskrat. 



The muskrat is generally distributed throughout the region 

 north to near the tree limit, but, like most of the small mammals, 

 was unusually rare during the summer of 1907. The only place 

 where we saw the animal in any numbers was the delta of the 



