1!)0 ON THE EXTINCT MAMMALIA OF 



In two fragments of the upper jaw from the same individual, rather advanced in 

 age, each contains the last two true molars, which have the following measurements : 



Lines. 



Antero-posterior diameter of second true molar, . . . .12 



Transverse " " " . . . .121 



Antero-posterior diameter of last true molar, , . . .10^ 



Transverse " " " . . . . lOi 



11. A number of isolated teeth and fragments. A last superior molar presents 

 two large conical tubercles or lobes at the fore part of its crown, and at its back part 

 two quite small ones. It measures ten lines antero-posteriorly and eleven lines 

 transversely. 



Of two last upper premolars, one is comparatively small. Their measurements are 

 as follow : 



Lines. Lines. 



Antero-posterior diameter of last upper premolar, . . . 10 J 9 



Transverse " " " . . . lOi 9 



The crown of one unworn canine measures 22 lines in length, 13 lines in breadth 

 at base, and 9 i in width. 



12. Fragments of several teeth, comparatively large, represented in figures 8 — 13, 

 plate X, of the Ancient Fauna of Nebraska, formerly attributed to another species 

 under the name of Archceotherium robtistum. These probably belonged to a male or 

 larger individual of Elotherium Mortoni. 



Other remains referable to Elotherium Mortoni. — Of other parts of the skeleton refer- 

 able to this animal I have the opportunity of examining an axis, and fragments of 

 several bones of the extremities, in the collections of Drs. Owens and Evans. 



The axis supposed to belong to Elotherium, Mortoni bears a resemblance to that of 

 the Peccary, though presenting some differences. The body inferiorly presents a 

 strong median keel, expanding posteriorly and separating a pair of broad deep 

 concavities. The posterior articular surface is a little wider than high, and is con- 

 cave. The odontoid process is strong, and marked below by the articular surface of 

 the atlas continuous with those of the anterior zygapophyses. The latter are wider 

 than high, and fonn an angle with the odontoid process of about 45°. They are 

 nearly flat transversely or obliquely, and convex from above downward. The trans- 

 verse process is feebly developed, and is pierced above from behind forward by the 

 foramen for the vertebral artery. The spinal canal, viewed in front, is obcordate. 



The measurements of the specimen are as follow : 



