78 
The supratemporal fossa is the same as in T. annectens , except that the 
parietal forms a greater part of the anterior border than it does in that species. 
The premaxilla resembles that element in T. annectens , though the 
anterior expansion is considerably greater. It is not, however, so greatly 
expanded as in Edmontosaurus regalis 1 or the Lance form figured by Cope 
as Diclonius mirabilis* . The antero-inferior extremity of the premaxilla 
is notched so as to leave five, well-marked, tooth-like projections. On 
the inferior surface, slightly behind these, is another series of less prominent 
but well-marked projections. The superior border of the anterior expansion 
of the premaxilla is recurved for a short distance so as to roof over a cavity 
of moderate size which opens backward. The floor of this cavity is smooth 
and the inner half is in the form of a depressed tract, separated from a 
sub-nasal depression by a broad buttress of bone which continues downward 
and outward from the upper limb of the premaxilla. The buttress gives 
considerable strength to the otherwise very thin bone. Penetrating the 
buttress and connecting the two depressions is a large, oval foramen, a 
cross-section of which is 20 mm. in its greatest diameter. This foramen 
is 50 mm. in length and is continued forward, into the anterior depressed 
tract, as a well-marked excavation which divides into three branches. 
The antero-inferior border of the foramen is pierced by an elliptical foramen 
35 mm. in length, which opens into the mouth. The backward prolonga- 
tion of the lower limb of the premaxilla reaches and overlaps the lachrymal, 
terminating opposite the midlength of that bone. The upper limb 
reaches beyond the midlength of the nasal aperture and is flanked by the 
anterior portion of the nasal for nearly one-half the length of the latter. 
The sub-nasal depression is the lower part of a well-defined area of which 
the nasal aperture is the centre. This was doubtless for the lodgment 
of the nasal gland. 
The nasal and prefrontal resemble those elements in T. annectens 
in form, proportion, and position, except that the prefrontal does not 
extend downward in advance of the orbit, quite so far as shown by Marsh. 8 
The inferior surface of the prefrontal is excavated so as to form a small 
pocket or recess at the supero-anterior border of the orbit. A similar 
pocket is present in the prefrontal of T . edmontoni and apparently also in 
T. annectens. 
The lachrymal is a moderately sized, irregularly shaped, flattened 
bone, that is wedged in between the prefrontal, nasal, premaxilla, and 
jugal, and infero-internally meets the palatine. The posterior border 
is free and makes up the central one-third of the anterior border of the 
orbital rim. The bone is not pierced by a lachrymal canal as in Edmonto- 
saurus regalis and Gryposaurus notabilis, though there is a slight excavation 
on the internal face which probably lodged the naso-lachrymal duct. 
The frontal region is large and flat except for a slight concavity on 
either side of the midline in the anterior portion, the greater part of the 
top of the head, between the orbits, being composed of these bones. They 
resemble those bones in T. annectens , but are longer in proportion to their 
breadth than in any other known genus of the Hadrosauridae . Postero- 
laterally the frontal forms the antero-lateral border of the supratemporal 
fossa and externally, toward the front, it extends outward between the 
i Loc. cit., figures 3 and 4. 
* Proc. Acad. Nat. Sci., Phila., vol. XXXV (1883). 
* Marsh, O. C.: "Dinosaurs of North America”, Washington, 1896, PI. LXXII. 
