0. C. Marsh — Description of Tertiary Artiodaetyles. 267 



By subsequent researches in the Uinta basin, the writer 

 secured many additional remains of all these three Artio- 

 daetyles, and in regard to Eomeryx, at least, nearly all the 

 important characters can thus be determined. These speci- 

 mens confirm in a decisive manner the original determination 

 of the essential features and affinities of the animal described 

 from the first fragmentary remains. 



The skull of Eomeryx has the same general form as that of 

 Agriochcerus, and the lower jaw and dentition are essentially 

 the same. As in that genus, there is no lachrymal fossa, and 

 the orbit is not closed behind. The complete dentition of 

 forty-four teeth is a primitive character to be expected from 

 a horizon lower than that of Agriochwrus. In this respect 

 and in several others, especially in the feet, Eomeryx shows a 

 nearer relationship to Oreodon, with which it certainly has 

 strong affinities. 



The upper molars, as shown above, natural size, in figure 18, 

 have the characteristic fifth lobe on the front of the crown, 

 as in the Ancodontidce, or Syopotamiis family, and this 

 feature alone, given in the original description of the genus, 

 served to distinguish Eomeryx from any allied forms in the 

 strata in which it was found. The lower molars are shown in 

 figure 22. 



19. 



Figure 1 9. — Upper teeth of Hyomeryx breviceps, Marsh ; seen from below. 

 Natural size. 



The limbs and feet of Eomeryx are of much interest. The 

 radius and ulna are distinct, and of nearly equal size. There 

 are four functional digits in the manus, and the first was also 

 represented, although of little use. In the hind limbs, the 

 fibula was slender, but complete. There were four functional 

 toes in the pes, all well developed, and a remnant, at least, of 

 the first was present. The digits were terminated by narrow 

 hoofs, similar to those in Oreodon. 



The genus Eomeryx, as thus determined, clearly represents 

 a distinct family, which may be called the Eomerieidce. This 

 group includes the genus Hyomeryx, described below, and 

 contains the oldest selenodont suillines in this country. It 

 had for its predecessors Helohyus and Homacodon from the 

 strata of the Dinoceras beds. 



