590 GEOLOGICAL SURVEY OF THE TERRITORIES. 



teriorridgecurvesroundattlie apex of the <, but is separated by a con- 

 siderable interruption from the posterior. The latter is shortened, and ter- 

 minates exteruailyin a conic tubercle, which approaches the outer extrem- 

 ity of the anterior ridge. In the last molar the posterior ridge is shorter, 

 nearly straight, terminating at a cone at each extremity. 



The canine is damaged, but was of large size, amounting in one or the 

 other of the jaws to a tusk. The probably superior is compressed, with 

 acute edges. The inner face gently convex, the outer more strongly so, 

 with an acute ridge on its anterior convexity, inclosing an open groove, 

 ■with the interior cutting edge. This surface of the dentine, when ex- 

 posed, has a transversely wrinkled character, but no trace of " engine- 

 turning" in the fractures. 



In the mandible, j)remolar and molar teeth are recognizable ; the char- 

 acter of the incisors remaining uncertain. As usual in the ungulates 

 they possess a relatively smaller transverse diameter than do the cor- 

 responding teeth of the maxillary. They change very materially in 

 form from the front to the terminus of the series, and, in connection 

 with the superior molars, are very instructive as to the generic connec- 

 tion of different types of dentition. 



The peculiarity of the premolars consists in the fact that, besides the 

 single external crescent exhibited by those of the upper jaw, they have 

 a rudimeutal second one in the position it should occupy in correspond- 

 ing teeth of Paleeosyops. The inner border of the crown is convex, and 

 extends from apex to apex of the crescents. There are no ciugula to 

 these teeth. The rudimental crescent diminishes anteriorly, its angle 

 becoming first obtuse, and then disappearing. Posteriorly the reverse 

 process takes place, and proportions increase. But in the last molars 

 they do not assume the proportions seen in PalceotJierium and allied 

 forms. They increase in the elevation of corresponding ridges of the 

 crescents and decrease in the others, so that the resultant form is nearly 

 like that of Dino titer ium or perhaps Lophiodon. The outer ridge of one 

 crescent appears as a cingulum, which sinks to the base of the crown 

 from the apex. This is rudimental in the genera just; mentioned. The 

 corresponding bounding ridge of the other crescent is reduced to a ru- 

 diment extending diagonally across the valley between the remaining 

 crests, as is seen in not a few genera of the Eocene. 



Measurements of the teeth. 



M. 



Total length of superior incisor , 057 



Length crown (inner face) superior incisor 015 



Width crown (oblique) superior incisor 020 



Width crown (oblique) inferior incisor 023 



Length crown (inner face) superior incisor 018 



Width canine .030 from tip 020 



Width posterior molar 039 



Length posterior molar 028 



Elevation posterior crest do 016 



W^idth anterior true molar 035 



Width premolar 028 



Length premolar 0215 



Len gth premolar, (first) 016 



Wid^h premolar, (first) 1 008 



Length premolar, (inferior) 024 



Width premolar, (inferior) 020 



Width penultimate lower molar 023 



Length penultimate lower molar 037 



In comparison with Bathmodon semicinctus, Cope, the crowns of the 

 premolars are of similar size, but more elevated. 



