IV. The very slender fpathetic or trochlear arises dorsally 

 " behind the optic lobes from under the cerebellum " ; and, 

 passing forwards above and beyond the optic nerve, it 

 enters the orbit to supply the obliquus superior muscle of 

 the eye. 



V. The *ttrigeminal issues (along with VII. and VIII.) 

 from the side of the medulla, anteriorly. Its branches are, 

 (1) The *superficial ophthalmic, which passes dorsally into 

 the orbit, forwards above the recti muscles, through the ol- 

 factory capsule and across the olfactory lobes to the dorsal 

 surface of the snout (sensory ampullae). Above it and 

 along with it (within a common sheath, except in Scyllium} 

 is the superficial ophthalmic branch of VII., which has a 

 similar distribution. On the floor of the orbit (and to- 

 gether forming a broad band, in Scyllium and Acanthias) 

 are (2) the *maxillary, which is connected with the inner 

 buccal of VII., and which supplies the ventral surface of 

 the snout, (3) the fmandibular, which innervates the lower 

 jaw, and (4) the ophthalmicus profundus (above the inner 

 buccal and on its inner side), which arises from the Gasserian 

 ganglion of the trigeminal root, and supplies a branch to 

 the eyeball, and passes forwards to the snout. This deep 

 ophthalmic nerve is " absent in Scyllium, at least as a 

 separate trunk. In Acanthias it runs ventral to the rectus 

 and obliquus superiores muscles, and in contact with the 

 eyeball." 



VI. The slender fabducens, arising from the medulla 

 almost mid - ventrally, below the roots of V. and VII., 

 supplies the rectus externus muscle of the eye. 



VII. The *ffacial. Its principal branches are, (1) The 

 superficial ophthalmic. See V. (2 and 3). The inner and 

 outer buccal, which pass under the eye to buccal ampullae. 

 (4) The large hyomandibular, which is a mixed nerve, 

 supplying the spiracle and the ampullae and muscles of the 

 mandibular and the hyoid arch. It passes outwards and 

 backwards behind the spiracle. Its chief branches are, 

 (a) the palatine, which goes obliquely forward across the 

 floor of the orbit, then downwards to the roof of the mouth, 

 (6) the prespiracular to the front of the spiracle, (c) the 

 postspiracular or hyoidean, which passes along or through 

 the front wall of the auditory capsule, then turns back 

 and goes downwards to the muscles and ampullae of the 

 hyoid arch ; and (d) the external mandibular, a branch 

 from the hyoidean, which passes behind and round the 



