2&0 • MB. W. E. COliLlNGE ON THE [^pf- 2, 



The Facial Group. — The only branch of the facial which I have 

 been able to satisfy myself actually innervates a portion of the 

 sensory canal system is the most posterior division of this group — 

 the ramus hyoideus — which runs in the ventral portion of the 

 preoperculum and innervates the canal which traverses that bone. 

 The ramus mandibularis (PI. XX. figs. 10, 11, r.m.) lies below the 

 mandibular branch of the trigeminal and does not enter into 

 relation with the branch of the canal. A small branch (PL XX, 

 tigs. 10, 11, .f) in some cases was in very close relationship with 

 the sub-orbital branch of the main canal, but no fibres could be 

 traced to the sensory organs. There would seem to be no inner- 

 vation to the upper portion of the canal in the preoperculum, neither 

 the ramus oticus nor the glossopharyngeal entering that region. 



The Vagus passes directly backwards, giving ofi a lateral branch 

 and other smaller branches. The lateralis vagi lies dorsally as far 

 back as the supraclavicle, passing beneath that bone, at a point 

 about at its upper third ; it then makes a downward curve to the 

 region of the lateral canal, which it innervates. 



V. S A L M O N I D .ffi. 



Salmo salab. 



General Besmjytion. 



The lateral canal commences at the base of the caudal fin and 

 passes anteriorly as a dermal canal. In its course forwards it 

 opens to the surface by a series of pores \\hich pass between the 

 scales, those scales in the region of the lateral canal being slightly 

 modified. 



It enters upon the head in the region of the pterotic bone, giving 

 off an occipital commissure and, anterior to this, the operculo- 

 mandibiilar branch. Posterior to tlie orbit it divides into supra- 

 and sub-orbital branches, the former passing some little distance 

 above the orbit and the latter through a series of canal-bones 

 forming the circumorbital ring. 



A number of variations in the branching and distribution of the 

 main canal of the head and its branches \^ ere noted in the various 

 specimens dissected. I shall first describe what I consider to be 

 the typical form, and then make mention of some of the variations 

 met with. 



Course of the Canals and Branches, 



1. The Lateral Canal is a dermal one like that in Esox; it 

 commences at the base of the caudal fin, and in its course forwards 

 opens to the surface by a series of pores which, as described above, 

 pass between the scales, there being a slight modification in those 

 scales in the region of the lateral canal. 



2. The Main Canal of the head is a fine canal enclosed within 

 a series of small drainpipe-like canal-bones (PI. XX. fig. 15), 

 not unlike those figm-ed and described in Polyodon (3. pi. 39. 

 fig' "^j <^)' I'' enters upon the region of the head above the 

 pterotic and gives off an occipital commissiu'e in the occipital 



