47 
postfrontal and jugal, and inferiorly by the jugal. The relative sizes of 
the orbits, narial opening, infratemporal fossae, and supratemporal fossae, 
may be expressed by the numbers 86, 56, 25, and 24 respectively. 
Post-temporal Fossce. In the occiput a deep transverse indentation 
or groove runs outward on either side from beneath the backward extension 
of the parietals under the lower border of the squamosal. This groove 
for some distance beneath the squamosal (Figure 6) represents the post- 
temporal fossae reduced vertically to such an extent as to oe virtually 
closed. In its more external part the lower border of the squamosal has 
an arched curve above the groove. Inferiorly the groove is bounded 
by the prootic and ?supra-occipital. A somewhat similar condition of 
these fossae is found in Iguanodon.^ 
Narial Opening. This opening has the form in lateral outline roughly 
of a lengthened oval, somewhat flattened below, and more rounded in 
front than behind, with a length nearly five times the height. The 
anterior and posterior ends are within the premaxillary and the nasal 
respectively. The superior margin is formed almost wholly by the nasal, 
and the inferior one principally by the premaxillary. The size of the 
opening is proportionate to the great anterior development of the pre- 
maxillaries. 
Foramen Magnum. This opening is large in comparison with the 
size of the brain-cavity. Its width is equal to half that of the cavity at 
the cerebrum and about equal to that across the medulla. It is nearly 
oval in outline, higher than wide, and narrowed slightly below. The 
vertical diameter is 50 mm. and the horizontal one at midheight about 
40 mm. It is bounded below by the basi-occipital, laterally by the ex- 
occipitals, and above apparently by the supra-occipital. Its upper outline 
is sharply defined by the transverse angulation formed by the junction of 
the descending roof of the brain-cavity and the lower surface of the supra- 
occipital. Laterally and inferiorly its exact boundary is not so clearly 
marked — being carried backward over the basi-occipital and between 
the condylar protrusions of the exoccipitals. Viewing the cranium from 
behind the opening is set deeply in the occiput with the supra-occipital 
extending nearly horizontally backward for a distance of fully 115 mm. 
from its upper rim. 
Cranial Foramina. Figures 26 and 27. The openings in the brain- 
case for the exit of the various nerves are well preserved in the paratype 
of Edm.ontosaurus. Their size and position are as depicted in Figure 26 
giving an external view from the right of the cranium proper. In Figure 
27 showing the cast of the brain-cavity in three aspects, lateral (A), superior 
(B), and inferior (C), the length of the foramina and their direction through 
the cranial walls are indicated. • 
The olfactory nerve opening (I) is bounded inferiorly and externally 
by the presphenoid. Whether the opening is roofed over by the frontals, 
or by the presphenoid, or by both, has not been determined as no sutures 
giving the desired information are preserved. The side walls of the 
presphenoid seem to curve inward over the opening, in which case the 
frontals would contribute to the formation of the roof only along the 
longitudinal midline. The opening is more than twice as wide as high. 
iQuatrifeme note sur les dinosauriens de Bernissart, par M. L. Dollo, Bull. Mus6e Royal d’Histoire Naturelle 
de Belgique, tome II, 1883, pp. 224-248, pis. IX and X. 
8329—4^ 
