1 66 ALUS. [Vol. XVIII. 



downward through that bone, leaving it near the hind end of its 

 long postero-dorsal edge. It then enters the suborbital bone and 

 runs nearly directly backward through it, entering the bone on its 

 external surface, some little distance beyond its anterior edge, and 

 usually leaving it on the same surface some little distance anterior 

 to the posterior edge of the bone. It then lies in the skin for a 

 short distance, turns sharply upward and enters the lower bone 

 of the postorbital series. Turning backward and upward in this 

 bone it leaves it at its upper edge, and then traverses the other 

 postorbital bones and the postfrontal, running at first upward, or 

 even upward and forward, then upward and backward, and then 

 upward and forward, around the hind edge of the orbit. 



At the dorsal edge of the postfrontal bone the canal enters and 

 traverses the deeper layers of the strip of skin that lies between 

 the postfrontal and the outer edge of that ridge of the frontal and 

 squamosal that forms the boundary between the dilatator and 

 temporal grooves. Having reached that ridge of bone it turns 

 sharply backward, and lies for a short distance in an open groove 

 on the outer edge of the ridge, the groove lying at first in the 

 frontal and then between the adjoining, overlapping edges of the 

 frontal and squamosal. At the hind end of the groove the canal 

 turns inward and backward between the overlapping frontal and 

 squamosal, and then enters that part of the ridge that is formed 

 by the squamosal alone, not having entered the frontal in any part. 

 Running backward in a curved line it reaches the deeper parts of 

 the ridge, and then, turning outward, issues from the bone at the 

 enlarged hind end of the ridge. There it enters the anterior end 

 of the lateral arm of the Y-shaped extrascapular, traverses that 

 arm, and then the shank of the bone, then the body of the supra- 

 scapular, and finally the supraclavicular, lying in a nearly hori- 

 zontal position in this part of its course. On leaving the supra- 

 clavicular it enters the first scale of the lateral line and becomes 

 the lateral canal of the body. 



While lying in the open groove in the ridge that separates the 

 dilatator and temporal grooves the canal forms an anastomosis 

 with the supraorbital canal ; near the hind end of the same ridge 

 it is joined by and anastomoses with the dorsal end of the pre- 

 opercular canal ; and at the anterior end of the shank of the extra- 



