286 



PROCEEDINGS OF THE ACADEMY OF 



[1894. 



Arvicola borealis. Toimtype, No. 1,908, ad. 9, Coll. of Acad. Nat. Sci., Phila. 

 (No. S,4(»8, Sm. Inst. : vid. Cones, N. A. Eod., p. 206, t. li). Fort Anderson, 

 North of Great Bear Lake (no date), E. McFarlane, Collector. 



Skidl. — Remarkably angular, 

 shallow and flattened, its anterior 

 jugal breadth exceeding the squa- 

 mosal, much as in Synaptomys. 

 Posterior ends of frontals pro- 

 duced in ii long, slender, strap- 

 shaped process, beginning just be- 

 hind the interorbital constriction, 

 between the projecting anterior 

 corners of the squamosal bones 

 and terminating in a dove-tailed 

 Fig. I. Skull and molar teeth of process between the acutely point- 



Aiz'icola dorca/is Rk'h. ■, i , i i , • 



^ TT«„„,. r.^^fi 1^ e ■ 4 / T +■+ ed and extended anterior corners 



a. Upper pronle ot cranium.* />. Lett 

 mandibular series. c. Left maxillary of the parietals. Interorbital 



^^"*?*^- constriction narrow, acutely com- 



pressed, its single median ridge depressed below the frontal plane. 

 Audital bulhe subtriangular, depressed, long and narrow. Denti- 

 tion as given (1. c.) for the subgenus Tetramerodon, of which, with 

 A. xanthogiiafhus and A. chrotorrhinus, it forms a typical represen- 

 tative in the lack of any attempt at a posterior inner fold, or angle, 

 in the middle upper molar. The anterior trefoil of the first lower 

 molar is less deeply indented than in any Arvicola I have examined. 

 The mandibles present no peculiar characters. An incipient groove 

 can be detected, almost evenly dividing the face of each upper in- 

 cisor. 



Arvicola drummoudi Aud. and Bach. 



Five specimens of meadow mice, three taken on the shores of Lac La 

 Hache, B. C, and two from the valley of the Kicking Horse River, 

 at Field, B. C, I had {n-eviously described in manuscript as new, 

 under the name Arvicola {Mynomes) microcephalus. 



The description of A. driimmondi (Aud. and Bach., Quad. N. 

 Anier., 1854, 166) I have since found to correspond so closely in 

 every particular with the characters of these specimens, it seems far 

 preferable to make tiiem the basis of a full restoration of driim- 



About one and one-half times natural size. 



