156 UPPER CRETACEOUS TELEOSTS 
actual head of the maxilla, in front of this depression, is large and rounded and 
articulates with both the mesethmoid and the vomer. The maxilla becomes 
flattened and deepened and reaches its greatest depth posteriorly. On the dorsal 
edge of the maxilla are two reduced supramaxillae. The anterior is the smaller 
and is pointed in front ; the posterior one has an antero-dorsal projection which lies 
along the dorsal edge of the anterior supramaxilla. All of the dermal upper jaw 
bones are smooth and unornamented. 
Mandible. The mandible is shown in lateral view in Text-figure 70. It is long 
and deepened posteriorly. The dentary forms the greater part of both dorsal and 
ventral edges, as well as the lateral face. On the ventro-lateral part of the dentary 
is a deep groove covered by a dorsal flange. Anteriorly this groove is closed and 
opens to the exterior through one or two large pores. The groove and tube con- 
tained the mandibular sensory canal. The oral border of the dentary bears 
numerous small teeth. 
The articular forms the posterior part of the jaw, with a transversely arranged, 
shallow articular facet. The posterior edge of the bone rises steeply from the 
facet to meet the dentary dorsally as the coronoid process. A small retroarticular 
process occurs behind the articular facet, and bears a lateral groove passing beneath 
the articular facet for the mandibular sensory canal. 
The angular is a triangular knob of bone applied to the posterior end of the 
articular below the retroarticular process. 
Opercular bones. The opercular bones are shown in lateral view in Text-figure 70. 
The operculum is large and deep with a straight, slightly thickened anterior edge, 
a rounded dorsal edge and an obliquely inclined ventral edge. The lateral face is 
unornamented and the opercular facet occurs near the upper limit of the anterior 
edge of the bone. The body scaling is continued on to the operculum. The 
suboperculum is also large and deep with its dorsal edge lying medial to the oper- 
culum. The bone is unornamented but the anterior edge is thickened and extended 
dorsally into a short process, medial to the operculum. The interoperculum is a 
prominent triangular bone lying medial to the ventral preopercular region. It is 
thin and unornamented and ends anteriorly just behind the retroarticular process. 
The preoperculum inclines forwards ventrally where it is considerably broadened. 
It ends dorsally below the head of the hyomandibular, with its leading edge resting 
against the posterior crest of the hyomandibular. Below the hyomandibular crest, 
the anterior edge of the preoperculum is expanded into a slight convexity. In the 
extreme ventral region the leading edge of the preoperculum rests against the 
posterior edge of the quadrate. The preopercular sensory canal ran in a groove with 
a prominent overhanging flange. Body scaling extends onto the posterior regions 
of the preoperculum, but not on to this flange. 
Pectoral girdle and fin. The supratemporal is never well preserved, but a projecting 
posterior portion appears to have housed a sensory canal. The post-temporal 
has a long curved dorsal limb articulating with the epiotic and an equally long 
ventral limb articulating with the posterior face of the neurocranium. The junction 
