164 UPPER CRETACEOUS.TELEOSTS 
insignificant retroarticular process occurs behind the facet and a groove on the lateral 
face of this process extends below the articular facet and passes forwards on the 
ventro-lateral surface of the articular. This groove carried the sensory canal. The 
posterior edge of the articular rises steeply from the facet to form the posterior part 
of the coronoid process. The angular is present as a small slip of bone applied to the 
postero-ventral region of the articular below the facet. The lateral face of the 
mandible is smooth and unornamented. 
Opercular bones. The opercular bones are shown in lateral view in Text-figures 
73 and 74. The preoperculum inclines forwards ventrally and dorsally ends just 
behind and below the head of the hyomandibular. The anterior edge of the pre- 
operculum lies against the posterior face of the hyomandibular crest. Ventral to the 
hyomandibular, the anterior edge of the preoperculum is expanded into a small 
convexity. Below this slight expansion the preoperculum lies against the rear edge 
of the quadrate. The preopercular sensory canal ran in a deep groove, open poster- 
iorly. A thin flange of bone overhangs this groove, neither the flange nor any other 
part of the bone is ornamented. 
The operculum is deeper than long with a straight anterior edge which terminates 
in an acute point antero-ventrally. The ventral edge is obliquely inclined, whereas 
the rest of the margin is smoothly rounded. The opercular facet occurs just within 
the upper half of the bone and is supported by a horizontal strengthening ridge 
which passes across the inner face of the operculum. The lateral face of the oper- 
culum is unornamented. 
The suboperculum is large with its dorsal edge lying medial to the operculum. It 
extends postero-dorsally for almost half of the depth of the operculum. The 
antero-dorsal corner of the suboperculum is produced into a small pointed process. 
The suboperculum is thin and delicate, except for a thickened anterior edge. 
The interoperculum is a roughly triangular sheet of bone with a straight posterior 
edge which abuts against the anterior edge of the suboperculum. The inter- 
operculum is thin and unornamented. 
Hyoid arch and branchiostegal rays. The ceratohyal is large and rectangular in 
shape, with a deep lateral groove running along its length. The groove indicates 
the course of the hyoidean artery and is interrupted by an elongate fenestra approxi- 
mately mid-way along the ceratohyal. There are two hypohyals. The exact 
number of branchiostegals is uncertain but they are arranged in two distinct groups. 
The ceratohyal supports several small, thin branchiostegal rays, possibly as many as 
five. The second group of rays arises from the epihyal and one from its junction 
with the ceratohyal. The branchiostegal rays on the epihyal are broad, long, 
flattened and four in number. 
Pectoral girdle and fin. The pectoral girdle is shown in lateral view in Text-figure 
75. The post-temporal has a long dorsal limb articulating with the epiotic and 
a shorter, thinner ventral limb passing antero-ventrally. The junction of the 
two limbs is somewhat flattened and expanded. No trace of a supratemporal 
could be found in any of the specimens. 
