5â^ il. H. POLLARD, 



the postfrontal and squamosal sense organ 7 is seen and behind it in 

 the centre of the squamosal is given oft" the opercular canal. The 

 8th sense organ lies near this spot and behind it also in the squa- 

 mosal the important branch leading to pore 8 passes ofi" downwards 

 and outwards towards the shoulder girdle. Sense organ 9 

 is the last belonging to the cranium. The system then continues on 

 as the lateral line of the body. 



Opercular canal. This canal passes downwards and outwards 

 in the squamosal in which it shows the pore marked 4 in the figure 

 (Fig. 6). So far and for a considerable space beyond no sense organ 

 occurs. The canal passes into the preoperculum and there lies the 

 sense organ marked 2. Close beneath this sense organ the hyoid and 

 operculum articulate with the hyomandibular. Close to this sense 

 organ opens pore 3. The canal continues further in the preoperculum 

 giving oft" pore 2 and containing sense organ 1. At the point of at- 

 tachment of the interoperculum it passes into the dermis and branches 

 dichotomously one branch, the anterior, opening shortly at pore 1 and 

 not continuing on into the lower jaw while the other branch, really 

 a continuation of the canal, runs backward and downward in 

 the interoperculum showing in that bone the sense organ marked 

 r in Fig. 6. From the interoperculum a short branch runs out below 

 the head and opens at pore 1'. This is represented diagrammatically 

 in the figure. 



Innervation. The sense organs of the infraorbital line are 

 innervated by branches representing the buccalis. Owing to poor pre- 

 servation of the material the nerve to the first sense organ could not 

 be traced. Sense organs 2 and 3 are supplied by one branch and 

 sense organs 4, 5 and 6 by their own branches. These nerves do 

 not run in common with the ophthalmicus superficialis. 



The supraorbital system is supplied by the ophthalmicus super- 

 ficialis in the normal manner. The first sense organ receives its nerve 

 from the median side while the 5th is supplied by a nerve which runs 

 intracranially. Organ 7 of the main line is supplied by the Ramus 

 oticus which as in other Siluroids arises independently from the sum- 

 mit of the ganglion plexus and passes through the bone in front of 

 the anterior semicircular canal of the ear. This branch crosses over 

 the branch marked x. The 8th sense organ is supplied by the Glosso- 

 pharyngeus and the !)th by the first branch of the Vagus. The main 

 lateral trunk of the Vagus continues on down the body giving oft' branches 

 to the respective sense organs. 



