MYOMOEPHA. 863 



base of the malar bone is much elevated and very oblique. The otic bulla 

 is flattened on the inner face, as in U. planifrons, and is not so compressed 

 as in the described specimen of E minor. The mastoid bone is convex pos- 

 teriorly, and supports an obtuse keel continuously with the inion. The 

 meatal tubes are broken off, but they were evidently not so long as in E. 

 planifrons. The postsquamosal foramen is large, and is near the posterior 

 lateral ridge of the squamosal bone. The frontal width of this species is less 

 than that of the E. planifrons and E. lamhdoideus, being just half of that of 

 the muzzle at its middle. In most of the crania the nasal bones do not ex- 

 tend so far posteriorly as the premaxillaries. In one of them the sagittal 

 crest is quite prominent ; in others more or less distinct traces of it are 

 visible. 



The molar teeth are directed obliquely backwards, the alveolus of the 

 first issuing below the anterior part of the orbit. The first superior molar 

 is the largest, but does not differ in form from the others; and the proportions 

 of the others diminish regularly posteriorly. The first inferior molar is a 

 little smaller than the second and third, and is about equal to the fourth ; 

 jts anterior column is contracted ; while the last molar is like the second and 

 third. The face of the inferior incisor is flat, and its enamel is smooth. 

 The external face of the jaw is bounded below by a strong angle as far 

 anteriorly as below the first molar. 



Measurements. 



M. 



Length of skull to incisive alveoli 041 



Width of skull at mastoids 020 



Width of skull between orbits 005 



Width of skull at middle of muzzle 010 



Elevation of skull from second molar Oil 



Length of molar series 007 



Length of first molar 002 



Width of first molar 002 



Length of crown of last molar 0015 



Width of crown of last molar 0015 



Length from M. 1 to infraorbital foramen 007 



Depth of mandibular ramus at M. 2 006 



Width efface of inferior incisor , 0016 



John Day River region of Oregon. 



