DAKOTA AND NEBRASKA. 199 



natural size; an upper view of tlie teeth, twice the size of nature, is given in figures 

 18, 19. The portion of the bone resembles the corresponding part in a Wolf more 

 than in any of the recent suilline animals. The first true molar (figures 17, c, 19), 

 retained in the fossil, is like those already described. 



The premolars (figures 17, 18, a, h) appear successively to have increased in size. 

 They have laterally compressed crowns, encircled by a basal ridge strongly developed 

 in front and behind, especially in the latter position, and moderately so at the sides. 

 The inner and outer surfaces are defined posteriorly by a sub-acute border descending 

 from the point, and dividing or splitting up towards the base. The front border is 

 more rounded. 



The surfaces of the crowns are strongly corrugated in relation with their size. 



The third premolar is wider in relation with its height than the second, and is 

 also proportionately thicker posteriorly. 



The fragment of an upper jaw with three teeth is represented in figure 15, twice 

 the natural size. A view of the triturating sui-faces of the teeth is given in figure 14, 

 twice the size of nature. Of the three teeth the last premolar is larger than the 

 succeeding true molars, and of these the first is the larger. 



The upper true molars (figure 14, h, c) have transversely trihedral crowns, and are 

 widest in this direction. The outer part of the crown is composed of a pair of simple 

 and regular conical eminences or lobes, festooned by a strong basal ridge. The inner 

 part of the crown is composed of a single conical lobe much larger than those exter- 

 nally, and it has a crescentoid ridge diverging from its summit on the sides out- 

 wardly. It is festooned in front and behind by a basal ridge continuous with that on 

 the outer part of the crown. Between the larger internal lobe and the outer ones 

 there is a pair of much smaller eminences, one placed at the fore, the other at the 

 back part of the crown. 



The crown of the last premolar (figure 14, a) consists of a transverse pair of lobes 

 resembling those of the true molars, but larger. They are enclosed by a basal lidge, 

 proportionately less well-developed than in the true molars, and, as in these, 

 interrupted internally. The inner and outer faces of the lobes are defined by 

 sub-acute ridges, ascending from the summit with an outward inclination. The basal 

 ridge develops a tubercle in front of the base of the outer lobe. 



The enamel of the upper teeth, as in the lower ones, is strongly corrugated or 

 wrinkled, in which respect, as well as in general appearance, the teeth of Leptochoerus 

 present some resemblance to those of PUolophus, of the eocene formation of England. 



The measurements of the specimens are as follow : 



