ESPECIALLY MYCTOPHOIDS 45 
the vertebral column. A slight dorso-laterally inclined ridge is produced on the 
exoccipital and is continued upwards by the epiotic as a prominent strut. The 
exoccipital also appears on the lateral face of the neurocranium since the bone is 
angled mesially, part lying on the posterior face of the neurocranium and part on the 
lateral face. The intercalar is attached to the outside of this angle. Laterally the 
exoccipital contacts the basioccipital ventrally, the prootic anteriorly and the 
pterotic dorsally. In the postero-ventral angle of the exoccipital the foramen which 
transmitted the vagus nerve is seen. This foramen is obscured in lateral aspect by a 
downwardly directed flange of the exoccipital. Slightly anterior to the vagus fora- 
men is the much smaller foramen for the glossopharyngeal nerve. 
The intercalar is a small flattened bone on the hind end of the lateral face of the 
neurocranium, elongated dorso-ventrally and ending below the posterior end of the 
hyomandibular facet. It does not take part in the composition of the wall of the 
cranial cavity, being entirely superficial in position and simply providing a point of 
articulation for the ventral limb of the large post-temporal bone. 
The pterotic has already been described in dorsal aspect ; laterally it forms the 
major part of the hyomandibular facet and is excavated above the facet to produce 
the posterior region of the dilatator fossa which is a prominent oval fenestra. The 
pterotic contacts the sphenotic and prootic in the anterior region of the hyomandibu- 
lar facet. 
The sphenotic is large and forms the postero-dorsal corner of the orbital region, the 
antero-dorsal part of the hyomandibular facet and the anterior half of the dilatator 
fossa. The hyomandibular facet is shallow posteriorly, anteriorly however it is a 
well defined cup-shaped facet formed dorsally of sphenotic and ventrally of prootic. 
Within the orbit the sphenotic contacts the prootic and the pleurosphenoid, and 
bears a small dorso-laterally directed foramen which transmitted the oticnerve into the 
sphenotic to innervate the infraorbital sensory canal. 
The pleurosphenoids, in the hind wall of the orbit, meet the frontals, sphenotics and 
prootics. The dorsal region of each pleurosphenoid is only ossified superficially and 
the more medial regions do not contact the frontal, the contact having been effected 
through the intervention of cartilage. The groove on the face of the bone, already 
mentioned in connection with the superficial ophthalmic nerves, passes up towards 
the ventral surface of the frontal. The course of the nerves along the frontal is in- 
dicated by a row of small foramina through which branches of the nerve passed to 
the supraorbital sensory canal. 
Hyopalatine bones. The hyopalatine bones are shown in medial view in Text- 
figure 20. The hyomandibular is short, broad and vertical in position, the quadrate 
condyle being immediately below the centre of the hyomandibular head. The head 
region is elongated, and inclined antero-ventrally. The anterior part of the head is 
thickened and associated with the anterior cup-shaped region of the hyomandibular 
facet. The remainder of the head is straight and narrow corresponding with the 
pterotic portion of the facet. The opercular process is not well defined and is merely 
a thickening of the posterior edge about mid-way down the bone. On the lateral 
face of the hyomandibular a crest runs postero-ventrally from the anterior region of 
