20 SYDNEY EVANS JOHNSON 



sides of the canal. The infraorbital receives its nerve supply 

 from the buccalis and oticus facialis. 



The hyomandibular canal begins at the ventral angle of the 

 bend of the infraorbital below the eye (figs. 1, 3). The nearly 

 straight canal passes backward to a point beyond the posterior 

 margin of the spiracle. Here it terminates in a slight upward 

 curve. Thirty or more tubules open from the canal to the ex- 

 terior. Its innervation is from the hyoid division of the R. 

 mandibularis externus VII. 



Mandibular canals. On each side of the lower jaw is a short 

 mandibular canal (fig. 3). The two opposite canals approach 

 each other anteriorly near the median line, but do not communi- 

 cate. These canals are innervated by branches of the mandib- 

 ular di\'ision of the mandibularis externus. 



The lateral canal (fig. 1) starts from its point of junction with 

 the supratemporal commissure and passes backward in prac- 

 tically a straight line, inclining slightly ventralwards, posteriorly. 

 Over the anal fin there is always a slight but characteristic 

 elevation of the canal for a short distance. Posteriorly the 

 lumen of the canal gradually decreases in diameter, and the 

 tubules become shorter. The lateral canal has approximately 

 140 tubules and they open to the surface in a line of pores which 

 hes considerably ventrad to the actual position of the canal 

 except near the posterior end, where the tubules are very short 

 and open directly to the sm^face opposite the canal. 



The lateral canal is innervated by the main division of a large 

 nerve, the N. lateralis, which is attached to the side of the 

 medulla oblongata anterior and superior to the first vagus 

 root. It should be noted in reference to figure 1 that the pores 

 and the pit organs are represented as if magnified while the 

 outlines of the fish are reduced. 



Supratemporal commissure (fig. 2). A short canal crosses 

 the supratemporal region immediately posterior to the openings 

 of the endolymphatic ducts. This is the supratemporal com- 

 missure and it communicates at each end with the lateral canal 

 of that side. In three different specimens 19, 22, and 23 tubules 

 were counted. They average about 1 mm. in length and open 



