SENSE ORGANS OF AMIURUS. 369 



ramus interims 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 opercidi, and <2) 

 a ramus ad M. adduct. arc. "palatini 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 mandibuloe. 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 levatores 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. — From the large ganglionic plexus in which lobes can be dis- 

 tinguished belonging to the different trunks (Fig. 13, PI. IV.) the 

 trunci branchiales vagi are given off. The 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. III. and / V. 



