60 NORTH AMERICAN MUSTELID.E. 



Puiorius, and much more obliquelj' truncated tlian in Pntorius, less so thaa 

 in Gnlo; frontal profile more or less concave. Nasal bones narrower in the 

 middle than at either end. General upi)er outline of skull moderately 

 arched. Production of mastoids and auditory bulLne and general prominence 

 of periotic region intermediate between Gulo and Putorins. Zygomatic arch 

 high behind (usually higher than in front) ; nowhere vertical, nor developing 

 a posterior convexity. Depth of emargi nation ^of palate greater than dis- 

 tance thence to the molars. Skull as a whole less massive than in either 

 Gulo or Putorlus. 



Vertebral formula. — According to Gerrard, the vertebr:e of If. martes, type 

 of the genus, is c. 7, d. 16, 1. 6, s. 3, cd. 18 or 19 ; other species of the genus 

 differ in the number of caudals. 



Size medium and large for this subfamily. Form moderately stout ; claws 

 strong, curved, acute. Tail longer than the head, bushy, cylindrical or taper- 

 ing. Soles densely furry, with naked pads. Pelage long and soft, but not 

 shaggy ; whole-colored, or nearly so, never whitening in winter. Progression 

 digitigrade. Habits highly arboreal as well as terrestrial ; not aquatic. 



This genus forms the link between Gulo and Futorius^ as will 

 be evident upon comparison of the diagnoses of the three. The 

 skull, however, is lighter than in either of the two other genera 

 of 2IusteUnce^ with more produced aud tapering rostrum ; in 

 height, relative to length or breadth, it is intermediate. The 

 species have a somewhat Fox-like or Cat-like superficial aspect, 

 rather than that appearance we usually associate with the name 

 of *' Weasel" , being much stouter-bodied, more copiously haired, 

 and bushier-tailed; one species, indeed, is commonly called 

 black " fox" or black " cat ". They appear to be more decid- 

 edly arboreal than the Weasels, spending much of their time in 

 trees, aud are not aquatic, like several of the Weasels proper. 

 They are agile and graceful in their movements; and, if not really 

 more active than the Weasels, their actions seem to possess 

 a quality of lightness and elasticity different from the writhing 

 and insinuative motions of the very slender-bodied, short-legged 

 Weasels. Although strictly carnivorous, predacious, and de- 

 structive to many kinds of small Mammals and Birds, they 

 appear less ferocious and bloodthirsty than the Weasels, whose 

 sanguinary impulses seem insatiable ; aud at times they exhibit 

 a playful and comparatively amiable disposition. 



The name of the genus is the Latin mustela or mustella, a 

 kind of Weasel; the word being apparently derived from, or 

 related to, the more general term mus.* Its adjectival deriva- 



* This seems to have included, besides Mice, various kinds of small de- 

 structive animals, such as now might be collectively referred to as "vermin". 

 Thus, mus pont'icus is supposed to have probably been an Ermine. The word 

 may be simply a long form of nms, like ma.cUla or axilla from mala and ala. 



