46 UPPER CRETACEOUS TELEOSTS 
enp.t 
pal enp hm.Vil hm 
ecp.t 
ecp 
pop 
den art 
20mm 
ciate) 
a | 
sym ¢ 
Fic. 20. Cimolichthys levesiensis Leidy. Hyopalatine and opercular bones and 
mandible of the right side in medial view. From B.M.N.H. P.1811. 
the head becoming lower and finally terminating near the ventral end of the bone. 
The preoperculum lies against the posterior face of this crest and is overlapped 
slightly by it. The hyomandibular tapers ventrally and its anterior extent is thin 
and covered laterally by the metapterygoid. The hyomandibular branch of the 
facial nerve entered the bone through a large foramen in the antero-dorsal region of 
the medial face immediately posterior to the anterior hyomandibular head. The 
nerve passed within the bone following a course parallel with that of the crest on the 
lateral face, and divided to give rise to the three main branches of the hyomandibular 
nerve. The opercular nerve left through a foramen above the opercular condyle in 
the angle between the main body of the hyomandibular and the lateral crest. The 
mandibular nerve passed through a foramen below the opercular condyle and here 
the posterior edge of the hyomandibular is excavated slightly. The mandibular 
nerve continued ventrally along a groove in the posterior edge of the hyomandibular. 
The hyoidean nerve may have left in the same region as the mandibular nerve since 
there is a second smaller foramen below the condyle. 
On the internal face of the quadrate a short stout bone is inclined forwards ven- 
trally and is slightly mesially constricted. This bone by its position suggests a 
symplectic, but in shape it resembles an interhyal. 
The quadrate is triangular with a prominent transverse condyle. The groove 
which housed the symplectic ends ventrally above the condylar region. The post- 
erior edge of the quadrate is slightly thickened and lies against the thickened edge 
of the lower part of the preoperculum. Anteriorly the quadrate overlaps, laterally, 
the posterior extent of the ectopterygoid and is firmly attached to it. 
