98 NORTH AMERICAN MUSTELID^. 



nal cusp. Anteorbital foramen presenting downward-forward (as in Miis- 

 tela; reverse of Gido), a mere orifice, not canal-like, and opening over the 

 last premolar (the opening more anterior in Giilo and Mustela). Skull as a 

 rule* little contracted at the middle ; the rostral portion extremely short, 

 stout, turgid, scarcely tapering, and much more vertically truncated than in 

 Gnlo or Mustcia ; frontal profile convex, and usually more nearly horizontal 

 than in Gulo or Mastela. Nasal bones widening forward from an acute base. 

 General outline of skull in profile scarcely arched— sometimes quite straight 

 and horizontal in most of its length. Production of mastoids and auditory 

 bulltB and general prominence of periotic region at a minimum ; the bullfe 

 flatter than in Mustela or Gulo, and scarcely so constricted across as to pro- 

 duce a tubular meatus. Zygomatic arch usually not higher behind than in 

 front, nowhere vertical nor developing a posterior convexity. Depth of 

 emargination of palate little if any greater, or less than, distance thence to 

 the molars. Skull as a whole more massive than in Mustela, though smaller. 

 Size medium and very small (including the smallest species of the whole 

 family). Body cylindrical, slender, often extremely so; legs very short; 

 tail long, terete, uniformly bushy or very slender and close-haired, with a 

 terminal pencil. Ears large, orbicular. Soles commonly furry. Pelage 

 usually close and short, whole-, or oftener, parti-colored ; turning white in 

 winter in Northern species. Progression digitigrade. Habits iudetermiu- 

 4ite — terrestrial, arboreal, or aquatic. 



The foregoing characters are drawn up from consideration of 

 the European and North American forms, and may require 

 some qualification, in ultimate details, to cover all the modifi- 

 cations of this extensive genus, containing, as it does, several 

 sections or groups of species, probably of subgeneric value. 

 From Gulo or Mustela it is at once distinguished by the differ- 

 ent dental formula. The skull, as compared with that of its 

 nearest ally, Mustela, differs notably in the shortness and 

 bluntness of the muzzle, position and direction of the ante- 

 orbital foramen, slight convexity of the upper profile, and other 

 points noted above. There is a decided difference in the char- 

 acter of the auditory bulla3, more readily perceived on compar- 

 ison than described 5 the bulLe are usually less inflated — some- 

 times quite flat, as in P. vison ; and even when, as in some 

 cases, the inflation of the basal portion is not much less than 

 in Mustela, we miss the constriction which in the latter genus 

 produces a well-determined tubular meatus. The skull of Fu- 

 tor'ius is decidedly heavier for its size than that of Mustela, in 

 this respect more like that of Gulo, though it is comparatively' 

 much flattened and otherwise dissimilar from the latter. 

 The name of the genus is from the Tiatin putor, a stench 



* In some species of Putorius, however, the constriction is as great as is 

 ever found in Mustela. 



