648 THE WASATCH FAUNA, 



I formerly identified my specimen with the Pliolophus sylvaticus of 

 Leidy, with which it nearly agrees in proportions. That species has a 

 wide fourth premolar, while this has a narrow one, as in the species of 

 Hyracotherium, although the crown is broken away so that I cannot see the 

 structure of the crown. The crown of the first true molar is represented 

 by Leidy as having an iutennediate tubercle, and a double anterior internal 

 cusp. Neither of these characters is seen in H. osbornianum. 



This species is dedicated to Mr. Henry Osborne, of Princeton, New 

 Jersey, one of the paleontologists of the College of New Jersey. 



The type specimen was found by myself on Black's Fork of Green 

 River, Wyoming Territory. 



Hyracotueeium angustidens Cope. 



Orohippus angustidens Cope. System. Cat. Vert. Eocene New Mexico, U. S. Geog. Snrvs. W. of 100th 

 Meridian, 1875, p. 22. Hyraeotherium angustidens Cope. Beport U. S. Ex. Snrv. W. of 100th Me- 

 ridian, IV, Part II, p. 265. 



Plate XLIXo; fig. 16. 



This small species was originally found by myself in the Wasatch 

 formation of New Mexico. I have not yet heard of its occurrence in the 

 Bridger beds, but it is abundant in the Wind River bad lands, and still 

 more so in those of the Big Horn, which are to be referred to the Wasatch 

 epoch. The specimens obtained are, as usual, chiefly lower jaws, but a 

 few maxillary bones and muzzles with teeth, were also found. While these 

 agree in general with those from New Mexico, they present variations in 

 proportions sufficient to require notice. 



In a specimen of variety C, below noted, the third and fourth pre- 

 molars and the first true molar are preserved. The former have consider- 

 able anteroposterior diameter, the third relatively the greatest. Its anterior 

 intermediate tubercle thus almost takes the position of a second internal 

 tubercle. There is a rudiment of a posterior intermediate tubercle on the 

 fourth premolar. On both premolars the external cusps are distinct from 

 each other. The anterior external cingular tubercle is well developed. 



In the ramus of another specimen of variety C, the anterior cusps of 

 the fourth premolar are equal, and the angle of the outer descends to form 



