ESPECIALLY MYCTOPHOIDS 61 
attaching to their medial edges. (A nasal component was not observed in the 
specimen and it may be that it is co-ossified with the mesethmoid.) The mesethmoid 
continues anteriorly in advance of the frontals and ends in an acute point. The 
supraorbital sensory canal ran within the frontal. In the snout region the sensory 
canal appears to have been directed towards the lateral region of the mesethmoid 
(possibly supporting the assumption that a nasal component is present in the 
mesethmoid). The infraorbital sensory canal crossed the dorsal surface of the 
sphenotic beneath the lateral flange of the frontal and joined with the otic branch of 
the infraorbital sensory canal. This latter branch passed on to the dorsal surface of 
the sphenotic. 
The pterotic is an elongate bone forming the postero-lateral border of the skull- 
roof, and bearing a shallow longitudinal crest inclined medially anteriorly. The otic 
branch of the infraorbital sensory canal passed within this crest and anteriorly the 
tube for the canal is clearly visible. Posteriorly the pterotic projects backwards for 
a considerable distance beyond the occipital border. Ventro-laterally the pterotic 
forms most of the hyomandibular facet. The pterotic contacts the sphenotic 
anteriorly, and the sphenotic contributes towards the anterior region of the hyo- 
mandibular facet. Postero-medially the pterotic joins the epiotic and parietal in the 
open groove which may represent the post-temporal fossa. The epiotic is poorly 
shown but does exhibit a slight thickening medial to the groove which provided an 
articulatory area for the dorsal limb of the post-temporal. 
The parasphenoid is visible below the orbit and is considerably expanded into 
ventro-lateral flanges which presumably were associated with the medial edges 
of the endopterygoids. The lateral ethmoid delimits the anterior orbital region and 
is a large bone attached ventrally to the postero-dorsal region of the palatine. 
Jaws and suspensorium. The jaw suspensorium is inclined slightly forwards 
ventrally so that the quadrate condyle is positioned below the centre of the post- 
orbital part of the skull. The head of the hyomandibular is considerably elongated, 
and its rear edge bears a shallow crest against which the anterior edge of the pre- 
operculum rested. Approximately one-third of the way down the bone this crest 
is joined by a second crest from the anterior region of the hyomandibular head. 
The combined crest so produced shallows and disappears at the ventral extremity of 
the hyomandibular. The anterior extent of the hyomandibular is a thin sheet of 
bone which is covered by the metapterygoid. The quadrate is triangular and stout 
with the condyle directed antero-ventrally. Anteriorly the quadrate is attached to 
the lateral face of the ectopterygoid. The association of the quadrate with the 
metapterygoid is difficult to interpret, the latter appearing to overlap part of the 
hyomandibular and to bear an obliquely inclined crest anteriorly. The ectoptery- 
goid expands slightly below the orbit where it is more thickened and prominent. It 
is assumed that this region ventrally bears teeth although none were clearly observed. 
Further forwards, below the lateral ethmoid, the ectopterygoid contacts the postero- 
ventral part of the palatine. An endopterygoid is attached to the medial region of 
the ectopterygoid and is inclined medially to associate with the parasphenoid in the 
roof of the mouth. The palatine is excessively elongated, deepest posteriorly and 
