DAKOTA AND NEBRASKA. 217 



breadth, the transverse diameter being an inch less than the vertical. The depth of 

 its posterior concavity is half an inch . 



Besides a number of fragments, together with several entire dorso-vertebral bodies 

 with detached epiphyses, of young animals, thei'e are under examination five adult 

 specimens of bodies of dorsal vertebraj. These are convex anteriorly and concave 

 posteriorly, and are short in comparison with their width, though not to the same 

 degree as in the proboscidean pachyderms. The largest of the specimens is two and 

 a half inches in length by about four inches in breadth, with the spinal canal about 

 two inches in width. The smallest sj^ecimen is two and a quarter inches long, and 

 three and three-quarter inches in breadth. The articular facets for the ribs, as in the 

 Elephant, are sustained on strong lateral processes, and are deeply concave. 



Several isolated heads of ribs present a spheroidal form, and have their facets 

 separated by wide sub-angular fosste. Thej' measure from an inch and a half to an 

 inch and three-fourths in diameter. 



Anterior extremities. — An isolated head of a right humerus is a segment of a sphere 

 with an ellipsoidal outline, and measures five and a half inches in its long diameter. 

 A specimen consisting of the upper extremity of a right humerus, with the head about 

 the same size as that just indicated, though too much mutilated to determine its 

 exact form, when perfect appears to have measured about a foot in circumference ten 

 inches below the head. Another specimen, consisting of the upper extremity of a 

 left humerus, has the head about five and a half inches in its long diameter, and the 

 short diameter about an inch less. The greatest breadth of the head and external 

 trochanter together has been over eight and a half inches. 



Six specimens, considerably mutilated, of distal ends of the humerus, exhibit a 

 radio-ulnar articulation nearly like that of the Rkmoceros. The largest specimen 

 measures about nine and a half inches in breadth at the tuberosities of the condyles, 

 and the radio-ulnar articulation is five inches in width. 



The bones of the fore-arm were as well developed in relation with each other as in 

 the Rhinoceros. 



The upper extremity of an ulna exhibits some resemblance to the corresponding 

 part in the latter animal. The bone, back of the articulation, is comparatively 

 broad and thin, fhe two sides are concave. The olecranon rises over seven 

 inches above the summit of the articulation, and is about five and a half inches 

 wide near its middle. Its summit, inclining downward and outwardly towards the 

 posterior border, is thick, tuberous, and deeply impressed by the insertion of the 

 tendon of the extensor cubiti. The articulation is divided into two unequal parts by 

 a deep notch externally, narrowing into a groove conducting inwardly and down- 

 ward to a deep irregular fossa, on the front aspect of the bone, separating the two 



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