474 ALLIS. (VoL. II. 
cross-commissure lies in the temporal region. Leaving the 
main infra-orbital canal in the extrascapula it runs slightly for- 
ward toward the top of the head, and meets there the end of 
the corresponding canal of the opposite side, thus forming a 
second connection between the two main lines, the first or 
anterior one lying on the top of the snout, as already described. 
These two are the only connections that are formed in Amia 
between the lateral systems of the opposite sides of the head. 
Leaving the several canals at irregular intervals, but at 
definite places, are the trunks of the different peripheral canal 
systems, each of which is represented on the outer surface of the 
bone by a distinct group of openings. 
Topography of the Peripheral Canal Systems. 
1. Infra-orbital Canal. — The infra-orbital canal, which is the 
direct continuation of the lateral line of the body, traverses in 
succession the supraclavicula, suprascapula, extrascapula, squa- 
mosal, postfrontal, post- and suborbitals, lachrymal, antorbital, 
and ethmoid, joining in this last bone the canal of the opposite 
side. Beginning at this point, in the middle line of the head, 
the canal first runs forward, outward, and downward to the outer 
anterior end of the arm of the V-shaped ethmoid, giving off at 
about two-thirds its course through the bone a branch which 
runs straight forward and upward to the surface of the bone, 
and has there a single large opening. This branch canal repre- 
sents the second peripheral system of the line, the first system 
having disappeared at the middle line of the head, as will be 
described later. It may be designated as trunk 2 (Fig. 41, 
Pl. XL.), and the corresponding pore or group of pores on the 
external surface as group 2. 
Leaving the ethmoid, the main canal turns sharply backward 
and upward, and entering the antorbital at its extreme anterior 
end, runs upward and backward along the middle line of the 
bone for about two-thirds its length. At this point, which is 
approximately above the articular end of the maxillary, it turns 
backward and leaves the bone at its hind margin. In the ant- 
orbital the canal gives off the trunks of four peripheral systems: 
trunk 3 at the beginning, trunk 4 at about one-third, and trunks 
5 and 6 close together at about two-thirds its course through 
