DAKOTA AND NEBRASKA. 41 



Opossum. They are strongly arched transversely, and are widest where they include 

 the ends of the anterior angular processes of the frontal bone. Between the latter 

 they form together a posterior triangle. In advance of their widest part they become 

 rapidly narrowed for a short distance, and then proceed onward of nearly uniform 

 breadth until, approaching the end of the nose, they slightly widen again. Their 

 free ends are notched at the middle, leaving the intermediate and lateral processes of 

 about equal length. 



The anterior nasal orifice has about the same form as in the Wolf, but is less 

 inclined. 



The upper extremity of the intermaxillaries extends back about as far as the 

 interval of the first and second premolars. 



The lachrymal bone contributes an elongated surface to the side of the face, 

 extending nearly the entire depth of the orbital entrance. At the orbital border 

 near its middle it is elevated into a short obtuse process. The face between the 

 position of the lachrymal process just mentioned and the iafra-orbital foramen is 

 somewhat depressed or slightly concave. 



The orbits. — The orbits are relatively about the size of those of the "Wolf, but they 

 have a broader floor and their inner wall is more concave. They are also better 

 defined by a more prominent, subacute ridge, proceeding from the superior orbito- 

 angular process obliquely backward, downward and inward. The latter process is 

 almost as well developed as that of the Black Bear. The inferior orbito-angular 

 process appears feebly developed. 



The orbital entrance has nearly the form of that of the Wolf, but the lower border 

 has a more downward direction from the front part. The direction of the entrance 

 is peculiar compared with that in ordinary carnivorous animals, being nearly vertical, 

 with a slight inclination forward and upward. 



The palatine region. — The hard palate expands to the back end of the alveolar 

 borders, and is strongly arched transversely compared with its condition in the Wolf. 

 Posteriorly, through the medium of the palate bones, it is prolonged into a cylindroid 

 canal, as in the Raccoon, Weasel, Deer, etc. 



The alveolar borders of the jaw diverge from the position of the premolars to their 

 posterior extremity, which appears to be almost continuous outwardly, and backward 

 with the zygoma. They gradually increase in depth posteriorly so as to form 

 prominent ridges, which greatly contribute to the transverse arching of the back part 

 of the hard palate. 



The posterior extremity of the alveolar ridge forms the anterior abutment of the 

 zygoma, and has inserted into it the sectorial molar, leaving no space sufficient for 

 the lodgement of a tubercular molar. It is separated from tlie hard palate and its 



6 



