No. 3.] LATERAL LINE OF AMIA. 483 
2. Lateral Line of the Body.— The first scale of the lateral 
line (Fig. 44, Pl. XL.) is always an irregular one. It is smaller 
than those immediately following it, much thickened, and 
roughly triangular in shape. It extends under the supraclavi- 
cula and lies in the direction of trunk 22-1, at an angle to the 
following scales of the line. The lateral canal enters it near its 
front edge, and leaves it on its inner surface, entering the next 
scale on its outer surface, and leaving it on the inner after trav- 
ersing approximately its middle third. It passes in the same 
way through the other scales of the line normally, giving off in 
each a peripheral canal system, similar to those found on the 
head. The trunk of each of these systems is given off at the 
extreme posterior end of the section of canal contained in the 
scale to which the system belongs. It lies in the direction of 
the canal and soon branches dichotomously, sending one branch 
upward and one downward, each with one or more openings 
on the outer surface of the scale. These openings lie near the 
hind edge of the scale, and are approximately concentric with 
it. The system of the first scale of the line is very irregular. 
It always has fewer surface openings than that of the next 
following scale, or no openings at all; the trunk is present, but 
in a more or less aborted condition. 
3. Supratemporal Cross-commissure. — The  supratemporal 
cross-commissure is given off medianward from the main canal, 
between trunks 18 and 19, in the extrascapula ; it traverses the 
length of this bone in about its middle line and joins, on the top 
of the head, the corresponding canal of the other side. In the 
full commissure there are two peripheral systems on each side 
and a double one in the middle. The two primary branches of 
this median system have become so widely separated in the 
adult that there are apparently three systems on each side of 
the head, the trunks of all of which run backward and laterally, 
with most of their branches directed backward and medianward. 
The median one of these three systems, although only a half- 
system, may be called No. 1, and it has in the specimen figured 
eight osseous openings. The next system, No. 2, has nineteen, 
and the lateral one, No. 3, twenty-five. 
4. Supra-orbital Line.— The supra-orbital canal begins near 
the anterior end of the nasal. It runs for a short distance 
backward and medianward, and then, turning sharply backward, 
