DAKOTA AND NEBRASKA. 183 



external pair and that antero-internally are the best developed and nearly equal, and 

 the intermediate ones of the two transverse rows are least developed. Posteriorly an 

 oblique ridge ascends from the summit of the postero-internal lobe to the base of that 

 postero-extern ally. 



The first true molar resembles the former, excepting that it has an additional ridge 

 festooning the outer side of the base of the postero-external lobe. 



As the conical lobes of the upper true molars do not extend more than half the 

 depth of the crown, they are obliterated when trituration has extended so far, leaving 

 broad exposed dentinal surfaces bordered with enam.el. 



Of the lower true molars the intermediate one is the largest, and the others are 

 nearly equal. Their crowns in outline are antero-posteriorly oblong oval and con- 

 stricted at the middle, as in the anterior pair of corresponding teeth of the Hog and 

 Peccary. The upper half of the crowns, forming the triturating surface in the 

 unworn teeth, is composed of two transverse pairs of conical lobes, confluent at base 

 and better developed than those of the upper molars. Posteriorly the crown is 

 bounded by a tubercle, intermediate to the back pair of lobes, and in front is bounded 

 by a narrow basal ridge. Portions of a basal ridge likewise diverge from the poste- 

 rior tubercle of the crowns of the anterior molars. In the last molar the posterior 

 tubercle is not better developed than in the teeth in advance, a condition one would 

 not have expected in an animal of such strong suilline character. 



A marked peculiarity in the lower true molars is observed in the tendency of the 

 antero-internal lobe to divide, as indicated by the cleft or grooved summit, or in other 

 words this lobe appears to be a connate pair. 



Of the upper premolars the first is the smallest, the third is the longest and widest, 

 and the fourth is the thickest. 



The fourth upper pi-emolar, smaller than the succeeding tooth, but longer, has a 

 three-sided crown, composed of a transverse pair of conical and basaly connate lobes. 

 These are like the corresponding ones of the true molars behind, but very much 

 larger and the outer lobe is about a third larger than the inner one. Posteriorly the 

 base of the lobes is embraced by a stout ridge, and one of less strength festoons the 

 base of the outer lobe in front, extending to the inner lobe. 



The anterior three upper premolars have simple, laterally compressed, conical 

 crowns, with a slight posterior curvature. Their front and back borders form sub- 

 acute indented ridges. The fore-part of the third, or largest of the premolars, is more 

 obtuse, or exhibits the indented ridge only towards the base of the crown, where this 

 likewise presents traces of a basal ridge, proceeding from the former one. 



The fourth premolar is close to the succeeding true molars, and the third is sepa- 

 rated from it by a narrow interval. The others are separated from the latter and each 

 other by rather wide intervals. The first one is situated obliquely in the jaw, as is 

 frequently the case in the Hog, close behind the canine tooth. 



