102 UPPER CRETACEOUS, TELEOSTS 
The sphenotic forms the postero-lateral corner of the orbit, meeting the pterotic 
behind and the frontal medially. The dorsal surface of the sphenotic is in part 
ornamented with the latticed tubercular ornamentation already noticed on the 
pterotic. 
The course of the sensory canals on the skull-roof is indicated by tubes within the 
bone and by grooves and depressions on the surface. The supraorbital sensory canal 
ran within a tube in the frontal opening anteriorly on the edge of the bone just 
posterior and lateral to the mesethmoid. Posteriorly this tube opens above the 
sphenotic in a triangular depression which is devoid of ornamentation. The main 
branch of the infraorbital sensory canal passed on to the dorsal surface of the 
sphenotic and entered a short tube within that bone which opens medially in the 
depression into which the supraorbital sensory canal passed. The otic branch of the 
infraorbital sensory canal entered the pterotic posteriorly through a pore at the 
anterior end of a short open groove. The sensory canal passed anteriorly within the 
pterotic and opened on to the dorsal surface of the sphenotic. Laterally, near 
the posterior end of the pterotic, a further foramen is present through which the 
preopercular sensory canal passed. A supratemporal canal was present running 
transversely across the skull-roof. This sensory canal connected with the otic 
branch of the infraorbital canal within the open groove on the posterior part of the 
pterotic. The canal passed medially in a tube within the parietal, but about mid- 
way along the bone the tube opens into a groove. This open groove is continuous 
across the dorsal surface of the supraoccipital from one parietal to the other. A 
further groove is seen in the mid-line of the supraoccipital connecting with and 
projecting back from the transverse groove. This groove seems to indicate that a 
further sensory canal was present in the mid-dorsal line of the body which connected 
with the supratemporal canal. 
The mesethmoid is a short broad bone which is well ossified and closely attached 
to the dorsal surface of the vomer. The palatines articulate with the lateral wings of 
the mesethmoid, while the premaxillary pedicels are joined in the mid-line and 
articulate with the anterior edge of the mesethmoid. 
Infraorbital bones. The infraorbitals are shown in lateral view in Text-figure 45. 
There are four infraorbitals and a large lachrymal in the circumorbital ring of bones. 
The bones decrease in size posteriorly and are unexpanded. Each bone in the ring 
carries a tube through which the infraorbital sensory canal ran. This tube opens 
occasionally on to the surface where it is simply a groove roofed by a flange of bone. 
The region of the sensory canal is ornamented with a single row of tubercles and the 
remainder of each infraorbital bone is sparsely tuberculated. The posterior bone of 
the series articulates with the sphenotic and received the sensory canal from the 
latter. The lachrymal is the anterior bone of the series and is longer than deep and 
dorsally bears a subocular shelf, but the remainder of the bones do not appear to 
exhibit this shelf. From the lachrymal an antero-dorsal projection articulates with 
the lateral ethmoid, while an anterior projection overlies the premaxilla laterally. 
The ventral border of the lachrymal is rounded and slightly roughened. The tube 
which contained the sensory canal runs within a dorsal ornamented thickened region, 
