1917] The Ottawa Naturalist 119 



different elements of the skull as they appear at the surface can be 

 readily seen. 



The dome-shaped prominence of the upper surface is formed by 

 the frontals, prefrontals, nasals and supraorbitals. The frontal con- 

 tribution is the largest of the four and occupies the greatest part 

 posteriorly and superiorly, the prefrontals reach upward laterally > 

 while the nasals assist anteriorly continuing backward slenderly 

 between the frontals to the highest point of the dome. The supra- 

 orbitals contribute to a minor extent laterally behind. 



The orbital opening is broadly oyate in outline with the more 

 pointed end downward. It is bounded by the supraorbital, the post- 

 frontal, the jugal, and the lachrymal, the last named element con- 

 tributing least, and the postfrontal and supraorbital nearly equally 

 to the formation of the rim. 



The lateral temporal fossa is more than three times as high as 

 wide and is enclosed in its lower half length by the jugal, and in the 

 upper half by the quadrate, the postfrontal, and, to a slight extent, the 

 squamosal. 



The prefrontal is largely developed and is more than three time? 

 as long as broad. It lies in advance of the supraorbital and the 

 lachrymal, is in contact above with the frontal, in front with the nasal, 

 and below with the premaxilla which it overlaps. 



The lachrymal is small and narrow, its extreme length being 

 three times its maximum breadth. Its narrow upper end underlies the 

 supraorbital while its posterior margin in its entirety enters into the 

 formation of the orbital rim. Inferiorly it is in contact with the jugal 

 and anteriorly with the prefrontal. Infero-anteriorly it is prolonged 

 narrowly downward between the jugal and the prefrontal, the extreme 

 end of the extension lying between the premaxilla and the maxilla. 



The jugal does not present any very unusual characteristics. It 

 is in contact with the quadrato-jugal and the quadrate behind, over- 

 lapping the former. In front it lies over a large surface of the 

 maxilla, and supero-anteriorly is in contact with the lachrymal for a 

 considerable distance. The end of its upwardly directed process, 

 forming the lower half of the slender postorbital bar, passes behind 

 the process from the postfrontal. 



The premaxilla is a large bone broadly expanded horizontally 

 outward in front where with its fellow it forms the edentulous anterior 

 termination of the cranium. Postero-exteriorly it extends upward 

 between the maxilla and the nasal as a long, narrow surface to meet 

 the lower end of the prefrontal which overlaps it. The front border of 

 the premaxilla curves outward and slightly backward from the midline 

 of the skull and is met at an obtuse angle by the outer border descend- 

 ing freely from its contact with the maxilla. The upper surface of the 

 bone is shallowly excavated in advance of the narial opening forming a 



