GEOLOGICAL SURVEY OF THE TEERITOEIES. 361 



been kindly placed at onr disposal by the gentlemen jnst named, we 

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



Hyracliyus approaches nearly the extinct genus Lophiodooi, first de- 

 scribed by Cuvier from remains found in the earlier Tertiary formations 

 of France and Germany. Lopliiodon 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. Hyracliyus has seven teeth to the molar series above and below, 

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



In Lo])Modon the last lower molar has a trilobed crown; in Hyra- 

 cliyus^ 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 pair of 

 inner lobes, connected by transverse ridges with the outer i)air, as in 

 the succeeding true molars. 



In Lopliiodon 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 Hyracliyus the two back upper premolars, corresponding with those 

 of Lopliiodon, 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 and the incisors of Hyracliyus hold the same relative 

 position as and resemble those of the Tapir. 



Hyracliyus agrarius. 



The species thus named was about two-thu-ds the size of the 

 South American Tapir. The molar series above and below contains 

 seven teeth. A series of upper molars measures of 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 3^ inches. Some remains from the same formation and local- 

 ity, described by Prof. Marsh and referred by him to Lopliiodon 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 Hyracliyus agrestis, 1 now suspect to be- 

 long to the same species as the foregoing. 



Hyracliyus modestus. 



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

 Prof. Hayden near Fort Bridger, and mentioned in his last report under 

 the name of Lopliiodon modestus. 



Hyracliyus 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^ lines. The depth of the jaw fragment is 1-J inches. The 

 species was intermediate in size to Hyracliyus agrarius and the South 

 American Tapir. 



Hyracliyus nanus. 



A smaller species than any of the preceding is indicated by two 

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



