MUSTELA 387 



orbit distinctly less than that of foramen. Postorbital process 

 short, not evidently directed backward. Zygomata more widely 

 spreading than in M. puforius, strongly and evenly bowed when 

 viewed from the side, the orbital process barely indicated and 

 posterior widening absent. Owing to shortness of postorbital 

 process and virtual absence of orbital process of zygoma, the 

 orbit is less margined with bone than in M.pHtorius. Brain-case 

 longer and narrower than in Mustela putorius, the outline when 

 viewed from above elongate ovate not distorted by the presence 

 of conspicuously projecting mastoid regions ; sagittal crest slight, 

 even in old individuals ; lambdoid crest moderately developed, 

 scarcely overhanging, the condyles usually visible from above. 

 Floor of brain-case nearly fl;it, though with the usual median 

 ridge and lateral and posterior depressions present. Auditory 

 bullae moderately inflated throughout, about three-quarters as 

 wide as long, nearly parallel sided, squarely truncate in front, 

 rounded behind, the meatus not tubular ; anterior extremity of 

 bulla not in contact with hamular, and separated from foramen 

 ovale by a broad nearly flat area, the length of which is 

 about one-half distance between foramina ; inner extremity of 

 glenoid surface marked off by a wide, shallow notch. Postorbital 

 region abruptly constricted, short, without indication of the 

 neck-like elongation which forms so conspicuous a feature of 

 the skull of M. putorius. Mandible with lower border slightly 

 convex, its posterior fourth somewhat elevated above general 

 outline ; angular process small but better developed than in 

 M. putorius. 



Teeth. — Except for their smaller size the teeth are essentially 

 like those of Mustela putorius. Enamel of lower canine not 

 rugose. Second upper premolar and third lower premolar more 

 compressed than in the larger animal, and with base of cusp 

 shorter, so that there is a slight but evident concavity or 

 flattening at both anterior and posterior base. Upper carnassial 

 with inner lobe projecting more forward than in M. putorius, so 

 that its anterior border extends nearly to level of that of outer 

 margin of tooth. Upper molar and posterior lower molar as in 

 Mustela putorius, but m^ with metacone more reduced, and m.2 

 with crown area distinctly smaller than that of heel of carnassial. 



Mustela erminea erminea Linnaeus. 



1758. [Mustela] erminea Linnaeus, Syst. Nat., i, 10th ed., p. 46 (Sweden). 

 1792. Mlzistela] erminea hybcrna Kerr, Anim. Kingd., p. 181 (name applied 



to the northern true ermine). 

 1816. M[;ustcla] herminea Oken, Lehrb. d. Naturgesch., iii, pt. 2, p. 1026 



(Renaming of erminea). 

 1827. [Mustela erminea] /3 maculata Billberg, Synopsis Faunae Scandinavise, 



p. 8 (Scandinavia). 

 1857. Fcetorius erminea Blasius, Saugethiere Deutschlands, p. 228 (part). 



2 c 2 



