22 UPPER CRETACEOUS TELEOSTS 
the posterior end of the pterotic through a small pore and continued anteriorly 
within the pterotic as the otic branch of the infraorbital sensory canal. The 
main infraorbital sensory canal traversed the antero-dorsal region of the sphen- 
otic and passed into the frontal, where it contacted the otic branch. The infraorbital 
canal and the supraorbital sensory canal may have contacted each other within the 
frontal. A supratemporal sensory canal crossed the roof of the skull on the parietal 
bones and entered the pterotic laterally above the post-temporal fossa. The pterotic 
in this region bears several flattened pores through one of which the supratemporal 
canal appears to have passed. Within the pterotic the supratemporal canal may 
have joined the otic branch of the infraorbital sensory canal. 
The mesethmoid appears to be small, forming the anteriormost region of the snout. 
The mesethmoid contacts the vomer, and their combined lateral surfaces provide the 
articulatory region for the internal face of the palatine. 
The lateral ethmoids are stout, well ossified bones firmly attached to the underside 
of the frontals and forming the anterior boundary ofthe orbit. Ventrally the lateral 
ethmoid is very irregular in outline, this area being filled with cartilage and providing 
the posterior suspensorial point for the palatine. 
The vomer is an extensive untoothed bone, attached to the mesethmoid anteriorly, 
and extending back below the parasphenoid as a broad flat plate. 
The parasphenoid is long and curved and anteriorly overlies the posterior shaft of 
the vomer. Below the orbit the dorsal surface of the parasphenoid bears a median 
longitudinal groove ending at the basisphenoid pedicel. This groove presumably 
served for the insertion of the ventral edge of a membranous interorbital septum. 
The ascending processes of the parasphenoid arise just posterior to the basisphenoid 
pedicel and pass vertically upwards to contact the prootics. The foramen through 
which the internal carotid artery passed lies at the base of the ascending process. 
Posteriorly the parasphenoid is reduced in depth and is flattened ventrally, where it 
contacts the ventro-lateral edges of the basioccipital. The parasphenoid ends below 
the occipital condyle, and the myodome opens posteriorly below the condyle. 
The basioccipital forms the lower half of the occipital condyle and contacts the 
exoccipitals above. The occipital condyle is practically square in outline with 
a prominent notochordal pit near to the dorsal edge of the basioccipital. The 
basioccipital, at its anterior end, contacts the prootic and the ascending process of the 
parasphenoid. Ventrally the basioccipital is grooved where it forms the roof of the 
posterior myodome. Just anterior to the condyle on the lateral face of the basi- 
occipital is a group of pits and ridges which may have marked the insertion of a 
ligament from the supracleithral region of the pectoral girdle but this is by no means 
certain. Internally the basioccipital forms the posterior parts of the otolith chambers 
and the posterior part of the myodome roof. The basioccipital above the myodome 
bears a prominent median longitudinal ridge which partially separates the otolith 
chambers. The basioccipital is inclined antero-dorsally above the myodome and 
contacts the posterior edges of the prootics. The otolith chambers are continued as 
recesses on the medial face of the prootics. 
