25 
it is relatively broad. Posteriorly it is in contact with the frontal which 
it overlaps to some extent. In its narrow posterior part it bounds the 
prefrontal inwardly, then suddenly expanding it extends downward in 
front of the prefrontal to the lachrymal and the posterior end of the lower 
premaxillary limb. Its contact with the lachrymal is short but it meets the 
premaxillary limb for a distance slightly over one-third of the latter’s 
length. Becoming slender again it passes forward above the narial opening 
to meet the upper premaxillary limb and continuing forward exterior to 
that process it ends thinly with a rounded outline just beyond the anterior 
end of the opening. Along the length of its contact with the premaxillary 
limb the nasal thins gradually to the front in the same ratio that the 
premaxillary limb narrows to its posterior termination, thus providing 
a uniform transverse breadth to the premaxillo-nasal portion of the roof 
of the narial opening. Behind the termination of the upper premaxillary 
limb the lower border of the nasal becomes decidedly protrudent, flatly 
arched at first and then descending backward, as the bone rapidly expands, 
to the lower premaxillary limb. Retired inward from the lower end of 
this protrudent border a spur of bone is sent forward by the nasal within 
the upper edge of the premaxillary limb, and in contact with the maxillary, 
increasing the extent of the naso-premaxillary contact and completing the 
enclosure of the posterior end of the narial opening within the nasal bone 
as seen in lateral aspect. 
Premaxillary. (Pmx.). Figures 3 and 4- This bone consists of an 
anterior portion expanding horizontally outward, a long, backwardly 
directed, gradually narrowing lower limb, and a relatively short upper 
limb also directed backward. As viewed externally it is in contact with 
the nasal, the lachrymal, and the maxillary. The two premaxillaries 
together give an anterior breadth to the snout apparently little less than 
the maximum breadth of the skull behind. The lower limb bounds the 
narial opening interiorly for three-fourths of the latter’s length, and con- 
tinuing beyond the posterior end of the opening, overlapping both the 
nasal and the lachrymal, it terminates some distance short of the pre- 
frontal. The upper limb passing back with increasing tenuity on the 
inner side of the nasal assists it in the formation of the supranarial bar to 
a point at about the midlength of the opening. The anterior end of the 
narial opening is within the premaxillary. As seen from above the front 
margin of the premaxillary curves outward and backward for about one- 
fourth of the bone’s total length; the outline is then inward and backward 
concavely in participation of the transverse compression of the skull at 
and above the maxilla. The front border of the anterior expansion of the 
premaxillary is recurved for some distance so as to roof over an extensive 
cavity which opens backward. The bone throughout is thin so that 
what outwardly might appear to be a heavy ending to the snout is in 
reality greatly lightened. The floor of the cavity is smooth and is con- 
tinued backward as an extensive, more or less depressed tract which is 
subdivided into three principal areas two of which together occupy the 
breadth of the bone at the mouth of the cavity and lead from it, and the 
third is situated beneath the narial opening. The inner anterior area is 
the most sunken of the three, is the least extensive, and is separated from 
the other two by a flange of bone which passes downward and slightly 
forward from the base of the upper limb in continuation of the upper 
