No. 3.] LATERAL LINE OF AMIA. 485 
part of the canal lying beyond the point of its anastomosis with 
the infra-orbital line ; two of its branches lie in the frontal, both 
directed backward and laterally, one reaching to the extreme 
hind edge of the bone, and the other sending a short branch 
beyond this bone into the squamosal. The two branches have 
six single and three double openings in the frontal and two in 
the squamosal. A third and principal branch is sent backward, 
directly in the line of the trunk, into the parietal, near its 
anterior and lateral corner. It runs straight backward in this 
bone, sending six branches to the surface, making seventeen 
openings in the entire system. 
5. Operculo-mandibular Line.— Close to the anterior end 
of each ramus of the mandible there is a single large opening 
which marks the beginning of the mandibular line. The tube 
from this opening leads backward and outward laterally into the 
anterior end of the mandibular canal, which, starting here, runs 
backward along the lower inner edge of the dentary. Leaving 
this bone, it enters the angular, and, turning upward near its 
hind end, passes out of it, and out of the upper surface of the 
mandible immediately in front of and above the articular pro- 
cess for the sympletic. It then turns sharply backward, and 
passing through the thick dermis between the angular and pre- 
operculum, enters this last bone on the dorsal surface of its 
lower anterior end. It passes through the entire length of this 
bone, lying near its inner deeper edge, and then passing again 
through a strip of dermis it enters the squamosal and unites 
with the infra-orbital canal. 
Along the mandibular part of the canal there are ten and a 
half peripheral systems, seven in the dentary and three and a 
half in the angular, most of them branching several times. 
Trunk 1 is a direct continuation forward of the main canal, 
which begins here, and has no connection whatever with the 
corresponding canal on the other side of the head. It has a 
large single opening at the front end of the dentary near the 
symphysis. Trunks 1 to 10 lie along the anterior horizontal 
part of the canal. No. 10 leaves it at the. point where it turns 
upward near the hind end of the angular, and has one branch 
running straight backward as a direct continuation of the main 
canal. In these ten systems there are seventy-four openings, 
twenty-eight of them plainly double. 
