DAKOTA AND NEBRASKA. 



353 



The first two teeth noticed, representing in the series the third and fourth premo- 

 lars, are unworn. In the first of the true molar series the summit and posterior 

 acute border of the principal internal lobe are worn so as to exhibit an exposed tract 

 of dentine, which is also exposed upon the anterior rudimental lobe of its anterior 

 acute border. 



The space occupied by the back six molars of Ictops is ten lines, being a little more 

 than in Leptldis. The measurements of the teeth are as follow : 



Antero-posterior diameter of third molar. 

 Transverse " " 



Antero-posterior diameter of fourth molar, 

 Transverse " " 



Antero-posterior diameter of fifth molar (estimated, 

 Transverse " " " 



Antero-posterior diameter of sixth molar (estimated). 

 Transverse " " " 



Antero-posterior diameter of seventh molar (estimated), 

 Transverse " " " 



Lines. 



2 



2i 



2 



2J 



II 



2i 



li 



li 



4d 



