120 



ON THE EXTINCT MAMMALIA OF 



entirely protruded. The interspaces, separating the inner and outer lobes in a 

 younger condition, have been completely obliterated in all the teeth, except traces in 

 the posterior two divisions of the last molar, as seen in figure 14. The inner surfaces 

 of the crowns, figure 13, exhibit ridges bounding the lobes with the intervening 

 spaces concave and smooth. A tubercle, an element of a basal ridge, exists only be- 

 tween the bottoms of the outer lobes. 



The measurements of the specimen are as follows : 



Length of the true molar series, 

 Antero-posterior diameter of last molar, 

 Transverse " " 



Antero-posterior diameter of second molar, 

 Transverse " " " 



Antero-posterior diameter of first molar. 

 Transverse " " 



Lines. 



34 



17 

 7i 

 9i 

 7 



7i 

 6i 



The isolated upper last true molar does not diifer in form from the corresponding 

 tooth of the smaller species. Its antero-i^osterior diameter is fourteen and a half 

 lines ; its transverse diameter ten and a half lines. 



Fragments of a skull of a young animal, apparently belonging to this species, ex- 

 hibit the following characters. 



The cranium with the same general form as in Oreodon, but with a relatively 

 shorter sagittal crest separating the temporal fossae. The crest divides into the di- 

 verging temporal ridges some distance back of the deeply notched anterior border of 

 the parietal. The forehead is relatively longer and more convex. The orbits are 

 closed by a post^orbital arch stronger than in Oreodon. The infra-orbital arch is 

 relatively deeper than in the latter. Lachrymal fossaj exist in front of the orbits. 

 The infra-orbital foramen is situated above the back part of the last temporary pre- 

 molar. In Oreodon at the same age it is above the interval of the latter and the 

 premolar in advance. The frontals are abruptly depressed approaching the root of 

 the nose, where the nasals, with parallel borders, are abruptly truncated. The 

 supra-orbital foramina are comparatively distant. The post-glenoid tubercle is very 

 flat antoro-posteriorly, quite linguaform in comparison with that of Oreodon. 



The teeth, preserved in one side of the jaw, consist of the three temporary molars, 

 the first and second permanent true molars, the first premolar and the canine. 



