ESPECIALLY MYCTOPHOIDS 113 
Posteriorly this tube opens above the sphenotic into a shallow triangular depression 
devoid of ornamentation. The infraorbital sensory canal crossed the dorso-lateral 
surface of the sphenotic before it entered the bone. It opened again more medially 
into the triangular depression already noticed in association with the supraorbital 
sensory canal. The otic branch of the infraorbital sensory canal entered the pterotic 
posteriorly and passed forwards within the bone also to open anteriorly into the 
triangular depression. A postero-lateral pore is visible in the pterotic and marked 
the passage of the preopercular sensory canal. A supratemporal sensory canal 
appears to have been present and may have connected with the otic branch of the 
infraorbital sensory canal within the posterior region of the pterotic. The sensory 
canal passed medially into the parietal where it opened into a groove on the surface. 
This groove is continuous across the supraoccipital, and it is assumed that the supra- 
temporal sensory canal was continued within this groove. 
The mesethmoid is a short broad bone produced laterally into wings which are 
attached to the dorsal surface of the vomer. The lateral edges of these wings serve 
as the articulatory points for the anterior regions of the palatine bones. The 
anterior edge of the mesethmoid is transversely arranged and the premaxillary 
pedicels articulated with it. 
The lateral ethmoids are small but stout bones, especially ventrally where they 
provide the posterior articulatory point for the palatine. Laterally the lateral 
ethmoid provides a further articulatory point for the lachrymal, and dorsally it is 
attached to the underside of the frontal. 
The vomer is separated from the mesethmoid postero-medially but attached to it 
anteriorly and laterally. The vomer has corresponding lateral wings to those seen 
on the mesethmoid. A short vomerine process extends back along the ventral 
surface of the parasphenoid. 
The parasphenoid is curved below the orbit and is little expanded ; the lateral 
regions being simply flattened and inclined ventrally producing a median, ventral 
longitudinal groove. The ascending process of the parasphenoid curves dorsally to 
meet the prootic, and has a thickened anterior edge. The foramen which trans- 
mitted the internal carotid artery into the base of the orbit lies near to the antero- 
ventral edge of the ascending process. The posterior part of the parasphenoid, 
below the myodome, bears a large mid-ventral, curved keel. The parasphenoid 
joins the ventro-lateral regions of the basioccipital and forms the floor and walls of 
the myodome. The myodome has a tiny posterior opening between two lateral 
sheets of parasphenoid below the occipital condyle and above the ventral paras- 
phenoid keel. 
The occipital condyle is circular and concave and composed of basioccipital 
ventrally and of the exoccipitals dorsally. The basioccipital contacts the exoccipitals 
dorsally, the parasphenoid ventrally and the prootics anteriorly. On the postero- 
lateral region of the bone near to the condyle is a group of pits and ridges. Internally 
the basioccipital forms the walls of the posterior part of the otolith chamber, and its 
ventral surface provides part of the roof of the myodome. Antero-dorsally the 
