The Lateral Sensory System in the Muraenidae. 131 



lateral end, on either side, the canal anastomoses not only with the 

 hind end of the main infraorbital but also with the anterior end of 

 the canal of the lateral line and with the dorsal end of the preoperculo- 

 mandibnlar canal. There is no primary tube or pore at the junction 

 of these four canals. 



The preoperculo-mandibular canal, beginning- as above stated, runs 

 downward through a long- tubular ossicle, and then traverses a short 

 portion of the preoperculum. The long tubular ossicle lodges one 

 sense organ of the line, the preoperculum probably lodging two sense 

 organs, though they were not actually found. Between the tubular 

 ossicle and the preoperculum a primary tube is given off, a second 

 tube being given off as the canal traverses the preoperculum, and a 

 third one as it issues from that bone. 



The canal then enters the mandible and traverses it nearly to 

 its anterior end, five primary tubes and pores being found in this 

 part of the canal, one of them being the anterior terminal tube and 

 pore of the line. 



Myrus vulgaris. 



The lateral canals of this fish (figs. 5 — 8) agree very closely with 

 those of Ophicthys, but both the nasal apertures of the fish lie near 

 the ventral edge of the upper lip, the anterior aperture lying on the 

 summit of a short tubular prolongation, while the posterior one is a 

 slit-like aperture resembling the corresponding aperture in Ophicthys. 

 Between the two apertures, and for a short distance posterior to the 

 l)Osterior one, the ventral edge of the lip is curiously dentated, the 

 little dermal papillae giving the lip the appearance of being toothed. 



The main infraorbital canal, as in Ophicthys, begins at a pore 



slightly posterior to the anterior nasal aperture. Running inward and 



Ijack^arti the canal enters at once the lachrymal, and, after giving 



off a primary tube and pore at the anterior edge of the posterior 



nasal passage, dips beneath that passage and reappears beyond it, 



where it gives off a third tube and pore. It then leaves the lachrymal 



and enters and traverses two suborbital bones, giving off a tube and 



a pore at the hind end of each of them. It then turns upward at 



* 9* 



