The Latero-Sensory Canals and Related Bones in Fishes. 441 



Thica ml gar it;. In this fish the canals, as shown by Andres [12], 

 seem to present exactly the same arrangement as in Moxostoma. 



No mandibular canal is given in this fish, this confirming its 

 absence in Moxostoma. 



Physostomi (Non-Ostariophysi). 



Muraenidae. In Conger, as I have shown [9\ the supraorbital 

 canal traverses a nasal bone but does not traverse a frontal; the 

 frontal section of the canal lying wholly superficial to the frontal 

 bone, and being simply enclosed in a fibrous tube that has become 

 largely chondrified. The canal anastomoses with the main infraorbital 

 either by its terminal or its penultimate primary tube, it could not 

 be definitely determined which, the anastomosis taking place at a 

 bend in the infraorbital canal where it passes from the dorsal one of 

 the infraorbital ossicles into the anterior end of the squamosal. 



The dorsal infraorbital ossicle is, in position, and in its relations 

 to the canals, a dermal postfi'ontal. 



The squamosal lodges two sense organs of the main line and both 

 of them are innervated by the ramus oticus, no organ innervated by 

 a postfacial nerve being found in the bone. The latero-sensory com- 

 ponent of the squamosal is thus morphologically shorter, posteriorly, 

 than that of any of the fishes so far discussed. Whether the lacking 

 component is wholly wanting in the fish, or is perhaps represented in 

 a short cylindrical ossicle that encloses a short section of the canal 

 that lies between the hind end of the squamosal and the supra- 

 temporal canal, could not be satisfactorily decided, for although no 

 sense organ was found related to this short cylindrical ossicle, its 

 positive absence could not be affirmed. 



The supratemporal canal, on each side, is enclosed in two cylind- 

 rical ossicles, each of which lodges a sense organ, and the canals of 

 opposite sides of the head unite in the mid-dorsal line to form a 

 complete commissure. The two enclosing ossicles represent two mesial 

 extrascapular elements; the lateral extrascapular being probably 

 represented in the ossicle that encloses the anterior organ of the 

 lateral line of the body. 



