74 UPPER CRETACEOUS TELEQSTS 
The frontals form almost the whole of the skull-roof, meeting in the mid-line in a 
distinct suture. A deviation of the suture to the right side of the roof is very 
noticeable in the posterior third of the frontal region. Posteriorly the frontals end 
near to the occipital border overlapping the anterior regions of the remainder of the 
roofing bones. The medial region of the roof is flat and relatively unornamented, 
and between the orbits there is a slight inter-orbital depression. The more lateral 
region of each frontal bears extremely prominent ridges which run in longitudinal 
and lateral directions from the centre of ossification. The major ridges bear an 
ornamentation of small bony tubercles. Several of the most prominent ridges 
pass forwards towards the snout region ; others pass laterally to terminate on the 
upper margin of the orbit. The ridges which extend posteriorly are arranged into 
a fan, the most lateral ridge passes straight back along the upper margin of the 
internal wall of the post-temporal fossa while the most medial ridge passes in 
towards the mid-line. The postero-lateral region of each frontal displays a V-shaped 
indentation of the upper ornamented layer. This indentation marks the forward 
extension of the unroofed post-temporal fossa. The frontal itself extends into the 
fossa forming the anterior regions of both the medial and lateral walls as well as 
the floor. The posterior half of the fossa is composed medially of parietal and 
laterally of pterotic. The frontal is applied to the dorsal surface of the sphenotic, 
this latter bone producing the upper hind limit of the orbit. Anteriorly the 
frontals taper from the orbits and contact the mesethmoid. 
The supraoccipital appears on the surface of the neurocranium as a small median 
bone with its anterior region overlain by the backward extension of the frontals, thus 
separating the parietals. Its internal extent is probably far greater than the out- 
ward appearance would indicate. As well as contacting the frontals and parietals, 
it also contacts the epiotics postero-laterally and the exoccipitals on the posterior 
face of the neurocranium. The supraoccipital crest is small, arising from the 
posterior face and not extending above the level of the skull-roof. On the surface of 
the supraoccipital, anterior to the origin of the crest, there is a shallow transverse 
groove crossing the complete width of the bone. 
The parietals are composed of two distinct regions, an anterior roughly triangular 
portion which is heavily ornamented and closely associated with the frontals ; and 
a smaller postero-lateral portion which is smooth and unornamented. In this 
posterior, smooth region, the epiotic and parietal join in the floor of a distinct 
transverse groove. The grooves are continuous with the transverse groove on the 
supraoccipital. Laterally the parietal forms the posterior half of the medial wall 
of the post-temporal fossa. 
The pterotic appears on the skull-roof lateral to the posterior region of the frontal. 
Anteriorly the pterotic is covered by a lateral extension of the frontal in the region 
of the post-temporal fossa. The pterotic is produced into a prominent vertical crest 
which forms the lateral wall and floor of the post-temporal fossa, and also part of the 
medial wall of the dilatator fossa. The pterotic contacts the sphenotic anteriorly 
and the suture is visible within the dilatator fossa. On the postero-dorsal edge of 
the pterotic crest a large foramen leads into a tube within the pterotic crest. A 
