348 GEOLOGICAL SUEVEY OF THE TEEEITOEIES. 



other oreodonts and the deer, and those which have long crowns, as 

 in the camel and sheep. 



The species of Merychyus, during the later tertiary period, appear 

 to have taken the place of the oreodons of the middle tertiary period. 

 The remains discovered appear to indicate three species of the genus. 



Merychyus elegans. — A small species, distinguished by this name, was 

 intermediate in size to Oreodon Culbertsoni and 0. gracilis, or was about the 

 size of the existing collared peccary. 



Merychyus medius. — This species, indicated by a few fragments, was 

 rather larger than the existing lama of South America. 



Merychyus major. — Fragments of jaws and teeth indicate this species 

 to have been about the size of Merycochazrus proprius, and nearly as large 

 as the existing camel. 



LEPTAUCHENIA. 



Another extinct genus of ruminants of the same family as the pre- 

 ceding, distinguished by the above name, was first indicated by a few 

 remains discovered by Professor Hayden in 1855, on one of the tributa- 

 ries of White Eiver, near Eagle Nest Butte, Dakota. Subsequently, 

 Professor Hayden, during his exploration of 1866, discovered additional 

 and more complete remains of the same genus on White Earth Creek, 

 a tributary of White Eiver, Dakota. The fossils are attributed by 

 Professor Hayden to the miocene formation. 



The skull of Leptauchenia has the general form and construction as 

 in the preceding genera of oreodonts, and the number, form, and con- 

 stitution of the teeth are nearly the same. 



The ear capsules are proportionately larger than in any of the other 

 members of the family. Large unossified spaces exist at the sides of 

 the face, extending from the forehead and in advance of the lachrymal 

 bones. Similar spaces exist in the living deer and lama, but not in the 

 other oreodonts so far as known. 



The true molar teeth or 'grinders of Leptauchenia most nearly resem- 

 ble those of Merychyus, but exhibit differences. The median buttress- 

 like ridges on the outer part of the upper grinders divide the crown to 

 the fangs more completely than in Merychyus; and in the lower grind- 

 ers the crown internally is divided by corresponding ridges, which are 

 nearly or quite obsolete in Merychyus. 



The fossil remains thus far discovered indicate the existence of three 

 species of Leptauchenia during the miocene period. Cotemporaneous 

 with the species of Oreodon and Merycochoerus they appear to have been 

 the predecessors of the species of Merychyus of the pliocene period. They 

 were all comparatively small, and have been distinguished by the follow- 

 ing names : 



Leptauchenia major. — The largest species of the genus was intermedi- 

 ate in size with Oreodon Culbertsoni and 0. gracilis. The length of its 

 skull was about five and three-quarter inches. 



Leptauchenia decora. — Rather smaller than 0. gracilis, had the skull 

 about four inches long. 



Leptauchenia nitida. — The smallest of the species was about the size 

 of the living musk deer. Its skull is three and a half inches in length. 



AGRIOCHCBRID^E. 



Another genus of extinct, hog-like ruminants, allied to the genera of 

 the preceding family, is nevertheless so peculiar that the author has 

 viewed it as the representative of a distinct family to which he has 



