0. 0. Marsh — Description of Miocene Mammalia. 411 



Perchoerus [Dicotyles) antiquus* 



On Plate X, figure 1, is shown a last upper molar tooth, 

 which may be provisionally referred to the genus Perchoerus 

 of Leidy. It is from the Miocene of Monmouth county, N. J., 

 from the same locality where was found the lower molar tooth 

 described by the writer as Dicotyles antiqtms, and the two 

 may be referred to the same species. The tooth is especially 

 noteworthy in itself from the complicated structure of its 

 crown, which approaches that seen in the existing suillines. 

 The lower molar tooth, the type of the species, has a crown of 

 simpler structure, and may be distinct. 



Colodon hixatus, Marsh. f 



The type specimen of the present genus and species is rep- 

 resented in part on Plate X, figures 2 and 3, which show the 

 entire dentition of the lower jaw. In the original description 

 cited above, it was shown that the present genus is probably 

 nearly allied to Zophiodon, but could be readily distinguished 

 from it by two inner cones on the upper premolars, and by the 

 absence of canines in the lower jaw. The same characters and 

 the presence of a posterior lobe on the last lower molar will 

 separate it from Hyrachyus. The type specimen is from the 

 Miocene of South Dakota. 



Rhinoceros matutinns, Marsh. J 



The lower molar tooth represented on Plate X, figure 4, is 

 from the Miocene of Monmouth county, N. J., and was found 

 in the same horizon and locality as the other specimens from 

 Xew Jersey described above. Its main interest lies in this 

 fact, the significance of which will be discussed later. The 

 tooth is the last lower molar of the right side, and while the 

 species appears to be distinct, the tooth agrees in its general 

 structure with the corresponding molars of allied forms from 

 the Pocky Mountains. 



All the type specimens above described are preserved in the 

 Yale Museum. These remains have a special interest when 

 considered in connection with the localities in which they were 

 found. Those from the West are from three definite horizons 

 in the Miocene, lying one above the other on the eastern flank 

 of the Pocky Mountains. Those from the Atlantic coast are 

 all from a single horizon in the same formation, and this 



* Proc. Phila. Acad., vol. xxii, p. 11, 1870. 

 f This Journal, vol. xxxix, p. 524, June, 1890. 

 JProc. Phila. Acad., vol. xxii, p. 3, 1870. 



