The Latero-Sensory Canals and Related Bones in Fishes. 409 



that this anastomosis with the latter canal, found in the adult, will 

 take place by the fusion of the terminal tube of the supraorbital 

 canal with that tube of the main infraorbital that lies at the point 

 where the latter canal bends sharply downward at the hind margin 

 of the eye. 



The main infraorbital canal begins in the middle line of the 

 ventral surface of the anterior end of the snout, at a single median 

 pore that is common to itself and its fellow of the opposite side. 

 Starting from there the canal runs at first laterally, on either side, 

 and then curves gradually backward along the ventro-mesial aspect 

 of the anterior nasal aperture. It then turns backward and upward 

 posterior to that aperture, and reaches a point near the postero- 

 ventral margin of the posterior aperture. The canal up to this point 

 apparently corresponds exactly to the anterior, ethmoidal section of 

 the canal of Amia, and it here apparently anastomoses by its hind 

 end with the second tube of the suborbital portion of the canal, 

 at a sharp bend in that canal, in exactly the manner that I have 

 shown and described for the canals in Amia [2, p. 471]. This anterior 

 section of the main infraorbital canal was separated, in the larval 

 Lepidosteus, into two portions, each of which contained three sense 

 organs, the two portions being continuous but not completely fused with 

 each other. 



The suborbital portion of the main infraorbital canal begins at 

 a pore that lies slightly posterior to the ventral edge of the posterior 

 nasal aperture, runs downward and slightly forward for a short 

 distance and then turns sharply backward, anastomosing at the bend 

 with the terminal tube of the antorbital section of the canal. From 

 there the suborbital canal runs directly backward along the edge of 

 the upper lip, turns slightly upw^ard at the hind end of the gape, 

 and then, turning downward and backward, encircles the ventral edge 

 of the eye. Posterior to the eye the canal is, in the specimen sectioned, 

 interrupted for a short distance, and one sense organ of the line is 

 here shown not yet enclosed in the canal. In the larva shown in the 

 figure the corresponding organ has apparently just been enclosed in a 

 short section of canal that is, as yet, independent both of the next 



