NERVES OF THE DOGFISH 347 



the latter; the other part passes posteriorly some distance be- 

 fore entering the visceral lobe (figs. 26 and 27). Within the 

 brain these two roots, sensory and motor, lie ventral to the ven- 

 tral-line root and dorsal to the anterior border of the great audi- 

 tory root (figs. 22 and 36). Outside the brain, accompanying 

 and dorsal to the motor and visceral sensory roots of the facialis, 

 is the posterior (ventral) lateral-line root, whose ganglion is situ- 

 ated on the hyomandibular trunk mostly distal to the geniculate 

 ganglion (fig. 24). 



3. The ramus ophthalmicus superficialis VII 



This large nerve is related to the anterior part of the dorsal 

 (anterior) lateral-line ganglion. As already stated, the ganglion 

 is so overgrown with fibers that few of the cells appear on the 

 exterior, but for the most part form a core that extends far out 

 in the nerve (figs. 5 to 11, 15 to 17, gos. VII). The nerve passes 

 anteriorly through the dorsal portion of the orbit, giving off 

 small nerves that pass dorsally through small foramina in the 

 supra-orbital crest of the cranium to supply supra-orbital canal 

 organs (fig. 50, os. VII). Rising higher in its anterior course 

 the main nerve at the anterior part of the orbit passes by its 

 own large foramen through the crest of the cranium to the top 

 of the head, where it courses anteriorly supplying supra-orbital 

 canal organs and the supra-orbital group of ampullae of Loren- 

 zini. The superficial ophthalmic has few large branches. The 

 largest one of these, given off shortly after the main nerve emerges 

 from the cranium, runs anteroventrally to supply the canal 

 organs situated in that part of the supra-orbital canal that runs 

 from the tip of the snout posteroventrally around to the ventral 

 side of the head to join the infra-orbital canal (figs. 35, 50 to 52, 

 eth.). Anteriorly the main nerve breaks up into numerous small 

 branches that supply canal organs and ampullae of Lorenzini 

 (figs. 1 to 4, os. VII). Accompanying the superficial ophthalmic 

 VII are two of the divisions (os. V 1 and os. V 2) of the super- 

 ficial ophthalmic V. These are so closely applied to the facialis 

 ramus as to appear like branches of the latter when given off. 



