ESPECIALLY MYCTOPHOIDS PATE 
The infraorbital sensory canal runs within a tube in the lachrymal and an antero- 
dorsal opening passed the sensory canal to the antorbital. The lachrymal extends 
back to the centre of the orbit where it becomes shallower. The remainder of 
the circumorbital ring is composed of five unexpanded infraorbitals, each bearing a 
flanged groove for the infraorbital sensory canal. 
Hyopalatine bones. The hyopalatine bones are shown in medial view in Text- 
figure 89. The hyomandibular is neither deep nor broad. The head of the bone is 
double and the two condyles are connected by a thin lamella of bone. The opercular 
process is large and extends postero-ventrally. The lateral face of the hyomandi- 
bular has a shallow crest arising from the anterior head region and curving postero- 
ventrally to run along the posterior edge of the bone. This crest disappears near 
the ventral end of the hyomandibular. The upper region of the preoperculum lies 
against the posterior edge of this crest. Ventrally the hyomandibular tapers and is 
terminated by cartilage. The anterior region is thin and overlain ventrally by the 
postero-dorsal edge of the metapterygoid. The hyomandibular branch of the facial 
nerve enters the bone through a small foramen close to the anterior region of the head. 
Within the bone the nerve divides and the opercular nerve passes through a foramen 
on the posterior edge of the bone while the hyoidean and mandibular branches leave 
through a larger foramen in the angle between the opercular process and the crest 
on the lateral face of the bone. 
The symplectic is long, thin and narrow and forwardly inclined. Its connection 
with the hyomandibular is cartilaginous and the interhyal also contacts this cartilage 
hm. hm Vil 
op.p. hm 
ecp 
op. 
pal mx.-p.p 
Q 
sop 
Saga Avo AION EN AMER RON nnniit =) 
pop emdirican 
den 
ie else 10mm 
q ang oe 
Fic. 89. Aulopus filamentosus. Hyopalatine and opercular bones and mandible of 
the left side in medial view. 
