40 NORTH AMERICAN MUSTELID^. 



agaiust the under canines. The other incisors are all alike, 

 smaller and evenly set ; all show indication of triiobation, with 

 a large middle and minute lateral lobes, best seen from behind, 

 where, at the point where the /teeth flatten toward the tips, 

 ridges divaricate, the termination of these ridges forming the 

 lateral lobes. The inferior incisors are irregularly set, the mid- 

 dle one on each side being crowded back out of the general 

 plane. The outermost pair are broader than the rest, and seem 

 longer, viewed from the front, since more of the tooth is exposed 

 from the alveolus. The next, partially displaced pair, viewed 

 from the front, seem the smallest of all ,• but this is due to their 

 position. Viewed from*behind, their size is seen to be much 

 greater than that of the middle pair. All the incisors are 

 obscurely lobate at end. The under canines are shorter, stouter, 

 and more curved than the upper ; most of their surface is stri- 

 ate. The anterior lower premolar, like the same tooth in the 

 upper jaw, is very small, displaced inward, and apposed against 

 the canine. The next premolar is markedl>r increased in size, 

 and set in the jaw with its longitudinal axis very oblique to the 

 general axis of dentition, as if turned partially around for want 

 of room. The next two premolars are much larger still and 

 massive ; they both show a single central pointed conical cusp, 

 whose sides are bevelled down all around to the rimmed base of 

 the tooth, but there is no indication of the secondary cusp half- 

 way up the back edge of the main cusp, as in Mustela pennanti, 

 martes, americana^ and perhaps all of this genus. Similarly, 

 on the great sectorial lower molar, there is no sign of a secondary 

 cusp on the inner face of the main cusp, as is so plainly seen in 

 M. marteSy and which also exists in less degree in M. pennanti^ 

 americana, and foina. These differences of the two back under 

 premolars and front under molar are, perhaps, the strongest 

 dental peculiarities of Gulo as compared with Mustela. Be- 

 sides this, the two main cusps of the anterior lower premolar 

 are subequal in size and elevation instead of very unequal, as 

 in Mustela., where the hinder one is much the highest. The 

 posterior tuberculous portion of this tooth is relatively much 

 smaller. As in allied genera, the back lower molar is small, 

 subcircular, tuberculous, not calling for special remark. 



In a large proportion of the skulls which come to hand, the 

 canines and sectorial teeth are found cracked, even split en- 

 tirely in two or broken off, apparently a result of the desperate 

 exertions the captured animals made to free themselves from 

 iron trai>s. 



