348 H. W. NORRIS AND SALLY P. HUGHES 



Their destination has been described. Arising from the ganglion 

 near the base of the r. oph. spf. VII are a few small much elongate 

 nerves that innervate the posterior part of the supraorbital canal. 

 Branches of the r. oph. spf. V (os. V 3) are closely associated with 

 some of them. 



4. The ramus buccalis VII 



The intimate association of this ramus with the ramus maxil- 

 laris V to form the truncus infra-orbitalis has been described. 

 Its distribution is to the sense-organs of the infra-orbital canal 

 and the associated ampullae of Lorenzini. From the ganglion 

 near the base of the ramus buccalis are given off a few small 

 nerves (fig. 50). One of these supplies the anterior portion of 

 the main lateral-line canal. Its distribution and relations will 

 be discussed under the head of the ramus oticus VII. The other 

 small nerves just mentioned collectively innervate the canal 

 organs of the postorbital section of the infra-orbital canal. The 

 ramus buccalis proper gives off few branches until it breaks up, 

 with the ramus maxillaris, into three main branches or rather, 

 three loose collections of small branches. Some of these supply 

 ampullae of Lorenzini only, but the most of them are distributed 

 to canal organs and ampullae indifferently. 



In Mustelus, as Allis has shown, the maxillary and mandibular 

 rami run for some distance with the ramus buccalis in a common 

 infra-orbital trunk. In this trunk the maxillary and mandibu- 

 lar sensory elements are completely merged, but always distinct 

 from the buccalis. 



5. The ramus oticus VII 



The ramus oticus, as mentioned in a preceding section, 

 enters a distinct ganglionic mass on the posterior distal part of 

 the buccal ganglion. The root fibers, however, unlike those of 

 the buccalis, seem to connect with the acusticum only, and not 

 with the lateral-line lobe. The canal organs which it supplies 

 lie in that part of the canal system which is the immediate pos- 

 terior continuation of the supra-orbital canal, between the latter 



