364 GEOLOGICAL SURVEY OF THE TEREITOEIES. 



NOTHARCTUS. 



Notharctus tenebrosus. 



This animal was inferred from a specimen consisting of a nearly com- 

 plete ramus of a lower jaw with most of the teeth. The fossil was 

 found imbedded in a grayish sandstone, at Black's Fork of Green Eiver, 

 during Prof. Hay den's exploration of 1870. In his " Preliminary Ee- 

 port" of last year I have placed it with the carnivora, but am now 

 inclined to doubt whether this is its true position. iliJ^otwithstanding 

 the carnivorous aspect of the canine tooth, I suspect the animal to have 

 been a pachyderm ; probably one of carnivorous habit. 



The teeth, consisting of incisors, a canine, and seven molars, form 

 together a nearly unbroken row. The canine has the ordinary form and 

 proportions of that of most carnivorous animals. 



In the original specimen the true molar teeth are much worn, so that 

 the characteristic marks are obliterated. In several fragments of jaws, 

 apparently of the same animal, obtained by Dr. Carter in the vicinity 

 of Fort Bridger, the molars are less worn, and therefore exhibit 

 somev of the anatomical characters. In these specimens the first and 

 second true molars have oblong crowns, constructed nearly as in JSyop- 

 sodus. As in this, the contiguous horns of the summits of the outer 

 lobes of the crown join the antero-internal lobe. In advance of the 

 latter are two small tubercles, the outer of which forms the termination 

 of the anterior arm of the summit of the antero-external lobe. The 

 characters of these teeth appear to agree with those assigned by Pro- 

 fessor Marsh to a genus of pachyderms, which he has named Limnotlie- 

 rium. 



The length of the dental series of the lower jaw of "Rotliarctus tenebrosus 

 is 19J lines. The true molars occupy a space of 9 lines. The animal 

 was about a third less in size than the Eaccoon, with which I at first 

 supposed it to be related. 



Notharctus rohustior. 



A small fragment of a lower jaw, containing the perfect second true 

 molar, with portions of the others, would appear to indicate a larger 

 species of Notharctus. The specimen was obtained by Prof. Hayden's 

 party, on Henry's Fork of Green Eiver. The entire tooth has the 

 same characters as the corresponding one of JV. tenebrosus. It measures 

 3^ lines fore and aft and 2 J lines transversely. In N. tenebrosus the 

 corresponding tooth measures in the same directions 2J by 2 lines. 



LiMNOTHERiuir, Marsh. 



Linmotherium tyrannus. Limnotherium elegans. 



Two pachyderms allied to the i)receding, but of smaller species, named 

 by Prof. Marsh from remains found in the Tertiary formation of 

 Wyoming. 



LOPHIOTHERIUM. 



Lophiotherium sylvaticum. 



Of this animal no additional remains have come under my notice 

 since the description of the jaw fragment, discovered by Prof. Hay den, 

 on Henry's Fork of Green Eiver, in 1869. The animal was about a 

 third less in size than the smaller li\dng Peccary. The true molar series 

 of the lower jaw occupies a space of 12|^ lines. 



