212 



It is especially remarkable for the great size of the ear-capsules compared 

 with those of the other species, being proportionately quite as large a.s those 

 in Agriochoerus. 



Of the multitude of fragments of jaws with teeth, portions of skulls, and 

 more or less complete skulls of Oreodon, which I have had the opportunity of 

 examining, by far the greater number are referable to the species O. Culbertsoni, 

 about a twentieth to O. gracilis, and one per centum to O. major. Specimens 

 exhibit more or less variation, generally of a comparatively trifling character, 

 but in some instances to such a degree as nearly to be distinctive enough for 

 other species, and in some cases as nearly to remove the distinctions between 

 the two species O. Culbertsoni and O. gracilis. Two specimens, presenting a 

 greater extent of variation than usual, have been suspected to represent hybrids 

 in the one case between O. Culbertsoni and O. gracilis, in the other case between 

 the former and O. major. With the view that they may be specifically dis- 

 tinct, they have been named O. affinis and O. hybridus. 



After a number of years, and after having seen many hundred specimens 

 referable to O. Culbertsoni, to my utter astonishment one of the last ones 

 received, consisting of the greater part of a skull, while agreeing in every 

 other respect with the ordinary form of O. Culbertsoni, possesses ear-capsules 

 as large as those of Agriochoerus. Looking upon this specimen as represent- 

 ing a species or an important variety, the name of O. bullatus was applied to 

 it in allusion to its large inflated ear-capsules. 



As the cranial portion of the skull of O. bullatus does not differ in size from 

 the specimens originally referred to Eucrotaphus, we are now uncertain 

 whether they pertained to O. bullatus or Agriochoerus. They correlate in 

 size, construction, and form equally well with either. 



Some remains from the Niobrara River, Nebraska, while clearly indicating 

 members of the same family as Oreodon, appeared to me to belong to two 

 different genera, to which the names of Merycochoerus and Merychj'us were 

 given. The recent discovery of additional remains of another species of 

 Merycochoerus, on the Sweetwater River, Wyoming, while rendering the 

 characters of the genus more obvious, rather tend to make the genus Mery- 

 chyus doubtful. 



The skull of Merycochoerus has the same general form and construction as 

 that of Oreodon, and the teeth agree in number, relative position, and consti- 

 tution. The crowns of the molar teeth in Oreodon are short and inserted by 



