The Lateral Line System in Siluroids. 533 



gives off a nerve which curves upwards and joins the great dorsal re- 

 current nerve of the Facialis. The Vagus continues on to supply the 

 lateral line of the body. 



The operculo-mandibular system receives its nerve supply from 

 the Ramus mandibularis facialis which does not divide into externus 

 and internus. This nerve passes out from its ganglion in company 

 with the Ramus hyoideus and both together run through a canal in 

 the hyoniandibular after leaving which they separate. The mandibu- 

 laris gives off branches regularly to the sense organs, the more poste- 

 rior curving slightly back, the rest forwards. In the opercular region 

 the nerve is enclosed in the same bone as the mucous canal but in the 

 lower jaw it lies just below or internally to the articular and dentary 

 bones. 



The last nerve to be described is the great recurrent dorsal branch 

 of the Facialis. This stoutest of all the nerves passes upwards and 

 backwards inclining medianly. In position it arises internally to the 

 anterior semicircular canal of the ear and a portion of its ganglion 

 occupies the common space enclosed by cartilage. The nerve runs 

 back into the parietal bone which it leaves before the posterior end 

 of the cranium is reached. It then takes a deeper course among the 

 body muscles and divides one portion passing on probably to supply 

 a dorsal canal, though this was not actually observed, while the other 

 becomes closely applied to the first spinal ganglion. No interchange 

 of fibres could be observed however and the nerve penetrates the stout 

 bone which runs out to support the shouldergirdle in Siluroids and 

 follows a direction towards the pectoral fin. 



In the parietal as before mentioned this recurrent nerve receives 

 the supratemporal branch from the Vagus. 



Callichthys paleatus. (Figs. 3 and 4.) 



A young specimen about 3 cm in length. 



The lateral line system is comparatively little developed though 

 at this stage there are no signs of actual degeneration. The number 

 of sense organs is small. 



Infraorbital system. This commences at a pore placed in 

 front of and below the eye which leads into a canal in the suborbital 

 bones. The first sense organ is situated below the anterior third of 

 the eye. The second and third pores open also below the eye 

 the second sense organ lying directly below its centre. The canal 



