GEOLOGICAL SURVEY OF THE TERRITORIES. 361 



been kindly placed at our disposal by tbe gentlemen just named, we 

 have been enabled more clearly to ascertain tlie relations of the genus. 



Hyrachyus approaches nearly the extinct genus Lophiodon, first de- 

 scribed by Cuvier from remains found in the earlier Tertiary formations 

 of France and Germany. Lophiodon was closely related with the exist- 

 ing Tapir. It possessed six molar teeth, in both the upper and lower 

 jaw, on each side. The Tapir has an additional tooth to the upper molar 

 series. Hyrachyus has seven teeth to the molar series above and below, 

 or seven above and six below, as in the Tapir. ^ 



In Lophiodon the last lower molar has a trilobed crown; in Hyrc{- 

 chyus, as in the Tapir, it has a bilobed crown. In the upper premolars 

 of the Tapir, except the first one, the crown presents a distinct x)air of 

 inner lobes, connected by transverse ridges with the outer pair, as in 

 the succeeding true molars. 



In Lophiodon the upper premolars, except the first, have a single lobe 

 to the inner part of the crown, associated by a single ridge with the 

 anterior of the outer pair of lobes. 



In Hyrachyus the two back upper premolars, corresponding with those 

 of Lophiodon^ have a single lobe to the inner part of the crown, asso- 

 ciated by a pair of ridges with both of the outer lobes. 



The canine teeth ancl the incisors of Hyrachyus hold the same relative 

 position as and resemble those of the Tapir. 



Hyrachyus agrarius. 



The species thus named was about two-thirds the size of the 

 South American Tapir. The molar series above and below contains 

 seven teeth. A series of upper molars measures 3f inches. A lower 

 jaw from another individual, from the back of the last molar to the 

 chin, measures 5J inches. The molar series of the same specimen 

 measures 3J inches. Some remains from the same formation and local- 

 ity, described by Prof. Marsh and referred by him to Lophiodon Baird- 

 ianus, probably belong to the same species. 



A species originally inferred to exist from a jaw specimen of a young 

 animal, and indicated in Prof. Hayden's preliminary report above 

 mentioned, under the name of Hyrachyus agrcstis, 1 now suspect to be- 

 long to the same species as the foregoing. 



Hyrachyus modestus. 



To a second species I now refer an upper molar tooth, obtained by 

 Prof. Hayden near Fort Bridger, and mentioned in his last rei^ort under 

 the name of Lophiodon modestus. 



Hyrachyus eximius. 



A larger species is inferred to have existed, from a small fragment of 

 a lower jaw of a mature animal discovered by Dr. Carter in the vicinity 

 of Fort Bridger. The specimen contains the last premolar and the 

 succeeding true molar. The former tooth is 7J lines fore and aft; the 

 latter 8:J lines. Tlie depth of the jaw fragment is IJ inches. The 

 species was intermediate in size to Hyrachyus agrarius and the South 

 American Tapir. 



Hyrachyus nanus. 



A smaller species than any of the ])receding is indicated by two 

 portions of lower jaws, one of which was obtained by Dr. Carter at 



