DAKOTA AND NEBRASKA. 273 



The two cofSn bones have nearly the same form and size, and differ from that of 

 the reconstructed foot in spreading less, or having a much less expanded base in re- 

 lation with their height. Their comparative measurements, together with that of 

 the reconstructed foot, are as follow : 



Lines. Lines. Lines. 



Height of anterior slope, . . . .30 



Breadth of lateral spread, . . . .51 



Extent of spread antero-posteriorly, , . .36 



Breadth of articular surface, . . . .27 



Projection of angles laterally beyond the articular surface, 12 



22. A pastern and coronary bone, apparently from the same individual, from the 

 Niobrara River. 



The pastern, somewhat smaller than the preceding, is not so wide in relation 

 with its thickness or antero-posterior diameter, and exhibits a rather greater dis- 

 proportion between the extremities. Its length, in the axis of the bone, is thirty- 

 three lines ; the breadth between the lateral tubercles, proxiraally, twenty-five lines ; 

 the breadth of the shaft at the middle is sixteen lines ; and the breadth of the distal 

 end is nineteen lines. 



The coronet differs but slightly from the smaller of the preceding specimens. 

 Its length in the axis is sixteen lines ; its breadth, between the upper lateral tuber- 

 cles, twenty-two lines ; the breadth of the proximal articular surface is twenty lines ; 

 and the breadth of the distal articular surface is nineteen lines. 



28. The lower extremity of a tibia much smaller than the corresponding portion of 

 the same bone of the Horse, and approaching in size that of the Ass. The specimen 

 is from the Niobrara River, and presents the following measuremen 



Breadth of lower end, ..... 



Antero-posterior diameter internally, 



Antero-posterior diameter externally, 



Antero-posterior diameter between the middle pyramidal eminences, and 



obliquely, . , . . . . . .21 



Breadth of articular surface, . . . . . .22 



s : 



Lines. 



. 30 

 . 19 

 . 14 



24. A median metatarsal bone, from the Niobrara River, intermediate in size to 



that of the recent Horse and the Ass, and probably pertaining to a Hipparion. It is 



both longer and proportionately narrower than the corresponding bone of Hlpparion 



gracile of Europe. It has the same form as in the recent Horse. Its measurements 



are as follow : 



35 



