fay 
SENSE ORGANS OF AMIURUS. 369 
ramus internus gains the inner aspect of the jaw where the R. 
externus is given off, and after passing under a cartilaginous loop 
ends in the mandibular barblets, teeth and mucous membrane, as 
well as in the intermandibular muscle which it helps to supply along 
with a motor filament from the facial. 
Facialis.—The mucous membrane lining the gill-cover has to be 
removed to expose the facial in its passage from its foramen of exit 
from the skull to its point of entry into the hyomandibular canal. 
In the exposed part it gives off (1) a ramus opercularis which runs 
backwards to the adductores hyomandibularis and operculi, and (2) 
a ramus ad M. adduct. arc. palatint which curves forwards round 
the posterior edge of that muscle, passes through the muscular sub- 
stance supplying it, and then enters the anterior part of the muscle 
where it is situated more superficially, and is joined by a branch of 
the ramus palatinus V. While in the hyomandibular canal a few 
branches escape to the muscles of the branchiostegal rays, and to the 
mucous membrane there. On escaping from the hyomandibular 
canal a stout ramus externus is given off which courses along the 
lower edge of the adductor mandibule to communicate with the r. 
ext. mandibularis as described above. In its course several small 
cutaneous filaments are detached, two of which effect communication 
with branches of the fifth emerging under the edge of the levator 
arcus palatini. 
The remainder of the seventh passes along the posterior border of 
the ceratohyal, and then into the fibres of the geniohyoid and inter- 
mandibular muscles. 
Glossopharyngeus.— I have already described this nerve as far as 
the formation of its ganglion. From this the nerve runs forward in 
contact with the skull and medial to all the devatores branchiarum, the 
most anterior of which it supplies. Before being distributed to the 
first branchial arch it gives a filament to the wedge of fat and con- 
nective tissue between the pharyngobranchials and the adductor arcus 
palatini. 
Vagus.—F rom the large ganglionic plexus in which lobes can be dis- 
tinguished belonging to the different trunks (Fig. 13, Pl. IV.) the 
trunci branchiales vayi are given off. he first and second trunks come 
off together, and are somewhat slenderer than the third and fourth. 
With the fifth come off the branches to the contractile palate and 
behind it a truncus intestinalis. Between tr. branch. /IJ. and IV. 
