DAKOTA AND NEBRASKA. 61 



obtained by Dr. F. V. Hayden, and purchased for the Museum of this Academy. It 

 is the smallest of the skulls of D. immcevus yet discovered, and probably belonged to 

 a female, as well as an aged individual as proved by the sectorial molars, in which 

 the crowns are nearly worn out. 



Besides being smaller, the face is proportionately somewhat shorter and narrower, 

 and the forehead less wide than in the preceding specimens. The orbits also are less 

 vertical, or have a more upward direction. 



The specimen is interesting from the fact of its exhibiting the marks of a conflict 

 some time anterior to the death of the animal, with an equally bloodthirsty creature. 

 On both sides of the forehead, above the orbits in front, and just back of the middle of 

 the temporal arches, there are four pits or depressions, the result of fracture, and just 

 such as might have been made by the opposed points of the canines of Hyamodon 

 horridus. Those over the orbits are the larger, in consequence of the greater breadth 

 of the cranium there presenting the first resistance. The edges of the fractured pits 

 are somewhat spon y, or exhibit the traces of reparatory action during life. The pits 

 have more the appearance of having been made by some equally powerful instrument, 

 such as the upp)er and lower canines of a Hycenodon, than by the more unequally 

 opposed weapons of one of its own kind. 



The figures 2, 3, 4, plate IV, of the molar teeth of D. primcevvrS, are taken from 

 the specimen of the greater part of a skull of a young adult. The series of perma- 

 nent molars had fully protruded, but the permanent canine had only partially 

 protruded. The specimen was discovered by Dr. Hayden, and was purchased for the 

 Museum of this Academy. 



Measurements of the two skulls oi Drepanodon primcbvus represented in the plate 

 accompanying the present memoir are as follows : 



Length of skull from occipital condyles to upper incisive alveoli, 6 inches. 7 inches. 



Distance from occipital condyles to end of post-orbital processes, . 



Length of sagittal crest, partially estimated. 



Width of temporal fossa from border of inion at the squamosal 



suture to the middle of temporal ridge of the frontal, 

 Height from glenoid cavity to sagittal crest, 



Breadth of inion at mastoid processes, .... 

 Length of occipital condyles, ..... 



Breadth of occipital foramen at back margin of the condyles, 

 Width of space between zygoma and palate bone, or of the outlet 



of the temporal fossa,. . . . . • 



Width from anterior glenoid margin to back of maxillary, 



Lines. 



Lines, 



40 



43 



30 



32 



31 



34 



31 



36 



29 



34 



9i 



10 



71 



8 





21 



14 



14 



