156 Edward Phelps Allis jr., 



The five sense organs of the supraorbital canal are all innervated 

 by branches of the ophthalmicus superficialis facialis, the course of 

 which nerve \\111 be fully described in a later work. 



Preoperculo-mandibular canal. 



The preoperculo-mandibular canal begins at a pore not far from 

 the symphysis of the mandible. 1'he connection with its fellow of 

 the opposite side, said by Collinge (No. 12) to be "formed by a short 

 canal in the cartilage", I could not find, nor can I determine what 

 cartilage could be here referred to. From the first pore of the line 

 a tube leads inward into the dentary and the canal then continues 

 backward to the hind edge of that bone, being in parts of its course 

 entirely enclosed in the bone, while in others it simply lies in a deep 

 groove on its outer surface. 



In its course through the dentary the canal gives off five primary 

 tubes, in addition to the anterior terminal one, each tube opening on 

 the outer surface of the head by a single pore, and the three posterior 

 tubes being enlarged to form considerable pouches. Posterior to the 

 dentary, between it and the angulary, there is another pouch which 

 represents the seventh primary tube of the line, and which had no 

 external opening in any of my specimens. Beyond this tube. No. 7, 

 the canal enters and traverses a deep groove on the outer surface of 

 the angulary, and immediately beyond that bone gives off a large 

 pouch, the eighth of the line, which opens on the outer surface by a 

 single pore. 



There are thus six tubes and pores in the dentary part of the 

 mandibular canal, one tube without a pore between the dentary and 

 the angulary, and one tube and pore between the angulary and the 

 ventral end of the preoperculum. In this length of canal there are 

 seven sense organs, six lying in the dentary and one in the angulary. 



Having left the mandible at its hind end, ventral to its articu- 

 lation with the quadrate, the canal comes into relation with the pre- 

 operculum, being in part wholly enclosed in that bone and in part 

 lying along its outer surface enclosed in firm connective tissue in 

 which there are small supporting pieces of bone. Dorsal to the pre- 



