DAKOTA AND NEBRASKA. 195 



genera, the one above named and that of the succeeding chapter, though I am not 

 positive that the remains of the former may not belong to the genus Palceochoerus, or 

 some of its allies, previously characterized from remains found in the miocene tertiary 

 of Europe. The indistinctness of detail with which many of the latter fossils are 

 depicted renders it often impracticable from the figures to make comparisons essential 

 to the determination of characters. 



Of the specimens referred to the genus and species above named, two consist of 

 fragments of lower jaws with teeth, and were formerly referred to the genus Palceo- 

 chmrus, with the name of P. prohus. 



One of the jaw fragments, represented in figure 20, plate XXI, contains a portion 

 of the last temporary molar, and the succeeding pair of permanent true molars with 

 the crowns fully protruded and almost unworn. From beneath the temporary molar 

 the fully developed crown of the last permanent premolar was removed, and is 

 represented in figures 22 and 23. These teeth bear a general resemblance in form, 

 construction and size to those of the recent Peccary, DicotyJes torqiiatus. They also 

 resemble those of Palceochoerus and Hyotherium, and perhaps to the exclusion of some 

 of the accompanying specimens may really belong to one of these genera. 



The first and second permanent true molars, figure 21, viewed from above appear 

 oblong-oval, with a moderate median constriction. From a continuous basis spring 

 four conical lobes, forming the triturating surface. The lobes are nearly equal in size, 

 and have moderately wrinkled sides. A strong basal ridge half the depth of the 

 crown is situated at its back part, and connects the bases of the contiguous lobes. A 

 thin ridge exists also at the fore part of the crown, and a festooned element of the 

 same occupies the interval of the outer lobes externally. A short distance below the 

 summits of the anterior lobes they are associated by a festooned ridge in front and 

 behind. Similar ridges descend from the postero-external lobe, of which the front 

 one ceases abruptly in the transverse valley of the crown, and the other joins a 

 median prominence of the posterior basal ridge. 



The unworn crown of the last permanent premolar, figures 22, 23, bears some 

 resemblance to the corresponding tooth of the Peccary, but is rather simpler in form, 

 and is less well-developed at the back part. The crown is broader than long, and 

 about half the thickness of the breadth. The principal pair of lobes are more closely 

 confluent than those corresponding to them in the Peccary, and form together a cone, 

 crossed antero-posteriorly by a shallow groove. At the base of the crown antero- 

 internally there is situated a comparatively large mammary tubercle, which is scarcely 

 represented by a basal ridge in the Peccary. Posteriorly a pair of mammillary 

 eminences form the base of the crown, of which the outer is almost twice the size 

 of the inner one. A thin basal ridge descends behind, from just below the summit of 

 the larger eminence, externally and internally. 



