No. 3.] LATERAL LINE OF AMIA. 481 
two anastomosing lines. There are seven such systems on the 
head of Amia, all of them essentially similar. Their pores 
multiply exactly as do those of a simple system, but the double 
trunk increases greatly in width along the canal, and the primary 
division of it is so deep that the trunk becomes practically a 
part of the canal (Cut 3, e. fg), its two primary branches ap- 
pearing as the trunks of separate systems. This is the con- 
dition found at the point of anastomosis of the infra-orbital and 
supra-orbital canals. The two systems that have fused here are 
Nos. 15 infra-orbital and 7 supra-orbital, and that part of the 
main canal lying between the frontal and postfrontal and extend- 
ing as far as the anterior edge of the squamosal is in reality the 
2 a 
Cut 3.— Diagrammatic representation of the formation of a double pore and 
system: a@, 0, and c, two pores approaching and fusing; d, double pore and tube; e 
and 7, the same, undergoing its first division; g, double system after second division 
of pore and tube. 
trunk of the double system. The anterior primary branch of 
this system (Fig. 40. Pl. XL.) runs forward and outward into 
the postfrontal, sending one branch medianward into the lateral 
edge of the frontal, and having thirty openings in all, three of 
them in the frontal. The other issues at the anterior edge of 
the squamosal, sending one branch forward and another back- 
ward, with ten openings in the postfrontal and thirteen in the 
squamosal. 
Trunk 16, the next regular one, is given off in the squamosal 
beyond the middle line of the bone, and is a short trunk directed 
laterally. It sends one long branch forward, overlapping the 
posterior branch of trunk 15, and a shorter one backward. It 
has twenty-nine openings, all lying near the lateral edge of the 
bone. Behind this trunk the main infra-orbital is joined by the 
