1895.] SEJfSOBY CAJf AL SYSTEM OF FISHES. 277 



The Sub-orhital Brancli passes down the anterior border of the 

 sphenotic and tlu-ough the post-orbital. At the commencement 

 of its course in the post-orbital it gives off the backwardly directed 

 branch terminating at pore 9. Continmng forwards it gives ofi 

 another similar branch in the sub-orbital bone, which terminates 

 at pore 10. It passes then into the lachrymal, opening by a pore 

 on the suture, and then into the maxilla, where it bifurcates and 

 terminates by the two pores 13 and 14 (fig. 1). 



The Operculo-^nandihvJar Braiich leaves the main canal of the 

 head in the anterior portion of the squamosal, from which it 

 passes into and through the pre- and inter-operculum ; in the 

 former it branches, and opens in the latter by pore 2. Leaving 

 the inter-operculum it becomes connected vrith the mandible by a 

 fine dermal canal. It traverses the whole length of the mandible 

 and in the most anterior portion meets with its fellow of the 

 opposite side. In its course from the main canal of the head to 

 the symphysis of the mandible it opens by eight pores. In 

 Chatostomus, according to Pollard (11. p. 538 and p. 543), the 

 mandibular branch is absent. 



3. The CoMiussuEE. — The only commissiire present in Glanas 

 nieuhofii is that in the f rentals, which establishes a connection 

 between the canals of either side of the head. PoUard (11. p. 527) 

 states that this commissure " is distinctly rudimentary and gives 

 very strongly the impression that it formerly united wit h its f eUow 

 of the opposite side." Again, on p. 542 op. cit. he states " it is a 

 complete commissure, but one becoming somewhat rudimentary." 

 He does not state what species he examined, but in neither of those 

 I have examined are there any signs of it becoming rudimentary. 

 I note further that he omits in his figure (11. pi. 35. fig. 1) any 

 sensory organs in this commissiire, one being present in Clarias 

 magur on either side of the median lines and innervated by the 

 ramus ophthalmicus superficiaUs of the trigeminal nerve. 



Injteeyation. 

 Clarias magur. 



The nerves innervating the sensory canal system are the tri- 

 geminal, facial, glossopharyngeal, and vagus. 



Of the trigeminal group the following branches innervate the 

 canals and sensory organs: — 



1. The ramus ophthalmicus superficiaUs. 



2. The ramus buccalis. 



3. The ramus oticus. 



1. The ramus ophthalmicus superficiaUs is the most dorsal branch 

 of the trigeminal and passes directly forwards. It gives off 

 branches to all the sense-organs lying between the pores 16 to 19 

 on the supra-orbital branch. Slightly posterior to the frontal 

 commissure a short branch passes off which innervates a sense- 

 prgan on the lateral border of the commissure, In the anterior 



