20 
underlaps the postfrontal. Postero-externally it sends downward and 
outward a large, laterally compressed process which, narrowing as it 
descends, curves slightly forward external to the para-occipital process of 
the exoccipital which supports it along its posterior curve. Postero- 
internally it extends inward behind the supratemporal fossa and is separated 
from its fellow only by the narrow, backward extension of the parietal 
ridge. Infero-externally tow^ard the front it develops a short, stout 
process which descends wdth a strong forward and outward inclination 
on the anterior face of the quadrate. Between this process and the large 
posterior one the bone is excavated for the reception of the head of the 
quadrate. 
Within the supratemporal fossa in the concavely and upwardly curved 
posterior face of the opening the squamosal in its inward course is above 
the parietal, the line of contact betw^een the two bones being at a con- 
siderable distance below the plane of the upper surface, of the skull. Intern- 
ally it abuts vertically against the narrow posterior extension of the parietal 
and completes its enclosure of the supratemporal opening behind by a 
short forward prolongation on to the median bar. 
The forward extension of the squamosal contributing to the formation 
of the supratemporal arcade is as broad as the portion of the postfrontal 
to the under surface of which it is applied. It is thin on its inner side and 
thickens outwardly to the cotylus for the quadrate. It extends forward 
to near the anterior border of the supratemporal fossa, and its thin inner 
edge together with the equally thin edge of the postfrontal forms the 
boundary of the opening externally. 
Viewing the skull from above the posterior outline of the squamosals 
betw^een the pendant process is almost transverse with only a slight curve 
forward. The squamosal in its upper surface curves slightly dowmward 
in its outward course from the parietal. Externally it bends rapidly 
downward to the descending outer face of the process. Postero-inferiorly 
the squamosals approach each other closely on either side of the parietal’s 
extremely narrow entry into the occiput. The posterior border of the 
squamosal for some distance outward from the parietal is heavy and 
rounded. Farther out, above the exoccipital, it becomes sharp-edged, 
at first ending freely but in the process closely applied to and coinciding 
with the par-occipital process. Except along its posterior border the 
squamosal process is free from the para-occipital process and separated 
from it by a narrow space. 
Measurements of the Squamosal of Edmontosaurus, Paratype, Cat. Xo. 2289. 
Mm. 
Length, from posterior border to anterior termination beneath the postfrontal 195 
Breadth, distance obliquely outward and downward from contact with parietal 
in posterior border to lower end of postero-external process, about 225 
Breadth in supratemporal arcade 80 
Thickness obliqueE upward and outward at midlength of cotylus 50 
Interno-posterior thickness (vertical) at contact with parietal 36 
Thickness of process at about its middepth and midbreadth 11 
Frontal. (E.). Figures 3, 4, 7,8,9,11, and 26. This element has a 
rather flat external surface of irregular shape, and longer than broad in 
about the proportion of 3 to 2. The suture along the midline between 
the pair is straight and well defined. Posteriorly the bone meets the 
