DAKOTA AND NEBRASKA. 



63 



Tipper molars. 



Breadth of crown of first premolar, . 

 Length " 



Breadth of crown of second " 

 Thickness " " " 



Length " " " 



Breadth of crown of sectorial molar, 

 Thickness " " " anteriorly 



Length " " " 



Breadth of crown of tubercular molar, 

 Length " " " 



Width, fore and aft, of ' 



Lcnoer molars. 



Breadth of crown of first premolar, 

 Thickness " " " 



Length " '•' " 



Breadth of crown of second " 

 Thickness " " " 



Length " " " 



Breadth of crown of sectorial molar, 

 Thickness " " " . 



Length of fore cusp of " " . 



Length of back cusp " " . 



Dr. Hayden's last collection of Mauvaises Torres fossils contains another skull of 

 D. primcBvus, without the lower jaw. It belonged to an adult, and exhibits the same 

 anatomical characters as the specimens already described. It is interesting from 

 its apparently bearing the marks of a deadly conflict with some other carnivore. 

 The forehead and cranium in the interparietal region are broken in from opposite 

 sides, apparently from the entrance of pointed instruments, such as the canine teeth 

 of the upper and lower jaws of the animal with which it may have been in combat. 

 The crown of the upper sectorial molar in the specimen is 9 ^ lines broad. 



21 



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ol lines. 



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51 





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41 





6 





Drepanodon occidentalis. 



Two small fragments of both sides of a lower jaw, found by Dr. Hayden, in his last 

 trip to the Mauvaises Torres of White Eiver, appear to indicate a species of Drepano- 

 don, or Macliairodus, larger than D. primceviis. 



The better of the two specimens, represented in figure 5, plate IV, contains the 



