ilUSTELUS L^VIS. 201 



ventral to the levator maxilla3 superioris. Having' readied 

 the outer surface of Csdo they there turn backward^ and then 

 break up and spread out on the outer surface of the muscle, 

 near its ventral end. They are apparently entirely sensory, 

 but they evidently correspond to the branches described and 

 figured by Vetter in Acanthias, one of which branches is said 

 to penetrate Csdo from its outer surface, and innervate it. 

 The fourth branch, in Mustelus, arises from the hind end of 

 the small ganglion, runs outward to the inner surface of the 

 muscle Csdo, and there separates into two parts, one of which 

 penetrates the muscle, and running backward is lost in it, 

 while the other turns backward along the inner surface of 

 the muscle, and there gradually disappears. This fourth 

 branch thus probably contains all the motor fibres destined 

 to the muscle Csd.,. What the ganglion fi-om which the four 

 branches arise may be I cannot determine, nor do I find any 

 description of anything that seems to correspond to it in any 

 of the works at my disposal. The ganglion cells have the 

 size and general appearance of those of the ciliary ganglion, 

 which may indicate that it is a sympathetic ganglion. 



Beyond this ganglion and the branches that arise from or 

 in connection with it no branch is given off by the truncus 

 facialis until it reaches the level of the distal end of the 

 hyomandibular, where the uerve separates into several 

 branches. One of these branches is destined to innervate 

 the sense organs of the hyomandibular lateral canal, and 

 another those of the mandibular lateral canal and the mandi- 

 bular group of ampullc\3. These two branches arise from the 

 truncus close together, if not as two parts of a single branch, 

 and they together constitute the ramus mandibularis externus 

 facialis of the fish. The branch destined to the organs of 

 the hyomandibular canal separates into two parts, both of 

 which run at first laterally and slightly downward, but soon 

 separate, one turning forward and the other backward, both 

 going exclusively to the sense organs of their canal, no 

 related ampulhe being found. The other branch or part of 

 the externus runs downward, forward, and mesially, along 



