1894.] NATURAI^ SCIENCES OF PHILADEI^PHIA. 285 



ing considerably behind base of nasals; the audital bullae are also 

 narrower, elonuate, and depressed. 



The dentition does not ditter from that of gapperi, but the other 

 characters of the skull of type, as above defined, show such con- 

 siderable differences from gapperi of eastern Canada that the ques- 

 tion of its specific value is yet an open one. 



Measurements. — Total length, 141 mm; tail vertebrre, 41; hind 

 foot, 19. Skull— Total length, 23-o; zygomatic width, 12-1; length 

 of nasals, 6*5; incisors to post-palatal notch, 10; interorbital con- 

 striction, 4-2; length of mandible, 18-2; width of mandible, (r2. 



One female (the type) was trapped on the banks of a small 

 stream flowing into Kootenai Lake, in the town limits of Nelson, in 

 the Selkirk Mountains. Two others were taken in the Rocky jNIouu- 

 tains, at Field, on the banks of the Kicking Horse River. 



Evotomys [^gapperil daicsoiii Merriam, the west Arctic representa- 

 tive, differs from saturatus in the opposite light phase of coloration, a 

 parallel case to that exhibited by the Hudsonian Chickadees, Paras 

 hudsonicKS, P. h. stoneyi, and P. h. columbianus. 



Notes on Boreal Arvicolas of Uncertain Status. 



Arvicola borealis Richardson. Rich., Zool. .Tour., No. 12, is^s, .517 ; Faun. Bor. 

 Anu-r., I, 1839. 127. And. and Bach., Quad, N. Amer., 1854, 134. 



Since the publication of the Monograph of North American Ro- 

 dentia, this species has been classed, on the authority of Dr. Coues, 

 as a subspecies of Arvicola j3ennsylvanicus. Several specimens from 

 the material examined by Dr. Coues in the preparation of his 

 monograph of the Arvicoliiue were subsequently presented to the 

 Academy of Natural Sciences. Among them I find two skins with 

 skulls and one specimen in alcohol enumerated in Dr. Coues' tabu- 

 lated lists of Arctic Arvicolas, which, after a careful study of 

 Richardson's two descriptions of A. borealis, I am convinced should 

 be referred to that species. The characters exhibited by these speci- 

 mens are those of an animal quite distinct from pennsylvanicus and 

 justify restoring borealis to the full specific rank originally given it. 



Audubon and Bachman (sup. cit.) have clearly restated the ex- 

 ternal characters of this vole from a personal examination of Rich- 

 ardson's types. 



Its cranial characters remain undefined, and may be described as 

 follow : — 



