45 
In advance of the curved process the bone narrows to a point. In the 
posterior two-thirds of its length it lessens but slightly in depth backward. 
In each of the three splenials available for study, viz., the two belonging 
to the naturally disarticulated skull. Cat. No. 2289, and the right one 
of Cat. No. 2288, the posterior end is missing, but, judging principally 
from the shape of the surangular in this region, it probably terminated 
with a rounded lateral outline as restored in the above figure. The bone 
is curved in conformity with the curve of the angular and surangular 
so that its inner surface is moderately concave in a longitudinal direction. 
Its superior border toward the front rises over, as already stated, 
and embraces the upper edge of the dentary. Its pointed anterior extension 
reaches forward and is applied to the dentary below the hindermost portion 
of the row of dental foramina. The surface of contact with the dentary 
extends slightly back of the spleniahs half-length. 
The splenial reaches farther back than the angular and is in contact 
interiorly with it for nearly the whole of the latter’s half-length. The^ 
surface of contact between the two is broadened and, with the increase in' 
area, strengthened by a ridge which extends outward along its length 
causing the lower external surface of the bone to be decidedly concave in 
a vertical direction. The upper surface of this ridge receives, and supports 
from below, at least in its more posterior part, the lower border of the 
articular. Anteriorly there is a space left between the splenial’s pointed 
extension and the angular which leads outwardly into the mandibular 
fossa. Postero-externally the bone for the whole of its depth is applied 
to the articular and passes beneath it by means of the ridge just mentioned. 
Measurements of Left Splenial of Edmontosaurus, Cat. No. 2289 {disarticulated 
skull). 
Length of bone preserved, measured along the inner curve 
Estimated total length 
Depth at midlength 
Len^h of sutural surface of contact with dentary 
Maximum breadth of same 
Mm. 
250 
304 
50 
172 
16 
Figure 25. Right angular of Edmontosaurus, Cat. No. 2289; I natural size. A, 
external aspect; B, internal aspect; dn, surface for dentary; sa, for surangular; sp, 
for splenial. 
Angular. (An.). Figures 20 and 25. This bone is long, narrow, 
and thin, and is in sutural contact with the splenial, the surangular, and 
8329—4 
